U.  S.  DEPARTMENT  OF  AGRICULTURE. 

BDRBAn  OF  SOILS— inWON  WIITSET,  Ciiet. 


220.^ 


/ 


SOIL  SURVEY  OF 
THE  MIDDLE  GILA  VALLEY  AREA, 

ARIZONA. 

D    001  108  858   0 


BY 


E.  C.  ECK^IANN,  In  Charge,  MARK  BALDWIN,  and 
E.  J.  CARPENTER. 


MACY  H.  LAPHAM,  Inspector,  Western  Division. 


[Advance  Sheets— Field  Operations  of  tlie  Bureau  of  Soils,  1917.] 

UCLA  SEL/Geology  Collection 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 

1920. 


BUREAU  OF  SOILS. 


Milton  Whitney,  Chief  of  Bureau. 
Albert  G.  Rice,  Chief  Clerks 

SOIL    SUBVEY. 

CuBTis  F.  Marbut,  In  Charge. 
G.  W.  Baumann,  Executive  Assistant. 

COMMITTEE  ON  THE  CORRELATION  AND  CLASSIFICATION   OF  SOILS. 

Curtis  F.  Marbut,  Chairman. 
Hugh  H.  Bennett,  Inspector,  Southern  Division. 
W.  Edward  Hearn,  Inspector,  Southern  Division. 
Thomas  D.  Rice,  Inspector,  Northern  Division. 
W.  E.  McLendon,  Inspector,  Nortliern  Division. 
Macy  H.  Lapham,  Inspector,  Western  Division. 

M.  W.  Patterson,  Secretary. 


U.  S.  DEPARTMENT  OF  AGRICULTURE. 

BUREAU  OF  SOILS— BIILTON  WHITNEY,  Chief. 


SOIL  SURVEY  OF 
THE  MIDDLE  GILA  VALLEY  AREA, 

ARIZONA. 


BY 


E.  C.  ECKAIANN,  In  Charge,  MAKK  BALDWIN,  and 
E.  J.  CARPENTER. 


MACY  H.  LAPHAM,  Inspector,  Western  Division. 


[Adyance  Sheets — Field  Operations  of  the  Bureau  of  Soils,  1917.] 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 

1920. 


LETTER  OF  TRANSMITTAL. 


U.  S  Department  or  Agricitlture, 

Bureau  of  Soils, 
Washington,  D.  6'.,  DeceTriher  15,  1919. 
Sir:  I  have  the  honor  to  transmit  herewith  the  manuscript  report 
and  map  covering  the  survey  of  the  Middle  Gila  Valley  Area, 
Arizona,  and  to  recommend  that  they  be  published  as  advance  sheets 
of  Field  Operations  of  the  Bureau  of  Soils,  1917,  as  authorized  by 
law. 

Respectfully, 

Milton  Whitney, 

Chief  of  Bureau, 
Hon.  D.  F.  Houston, 

Secretary  of  Agriculture, 


CONTENTS. 

Page. 
Soil   Srm-EY  of  the  Middle   Gila   Valley  Akea,   Arizona,     By   E.   C. 

EcKMAN,  In  Charge,  Mark  Baldwin,  and  E.  J.  Carpenter 5 

Description  of  tlie  area 5 

Climate 8 

Agriculture 11 

Soils 16 

Pinal  gravelly  sandy  loam 19 

Mohave  sandy  loam 20 

Mohave  fine  sandy  loam 21 

McClellan   loam 22 

McClellan   clay  loam 24 

Gila  fine  sand ^ 25 

Gila  silty  clay  loam 26 

Pima  clay 28 

Rough   stony    land 29 

Riverwash _. 29 

Irrigation 30 

Drainage 31 

Alkali : 32 

Summary 35 


ILLUSTRATIONS. 


PLATES. 


Page. 
Plate    I.  Fig.  1. — View  overlooking  desert  soils  grouped  in  the  Mohave 

series.     Fig.  2. — Alfalfa  on  Mohave  sandy  loam,  near  Casa 

Grande 16 

II.  Fig.  1. — View  in  Gila  River  bottoms  near  Florence.     Fig.  2. — 

Alfalfa  on  Gila  silty  clay  loam,  near  Florence 16 

colored  plate. 

Plate  A.  Alkali  map.  Middle  Gila  Valley  sheet 32 

FIGLTIE. 

I'iG.  1.  Sketch  map  showing  location  of  the  Middle  Gila   Valley  Area, 

Arizona 5 

MAP. 

Soil  map,  Middle  Gila  Valley  sheet,  Arizona. 

3 


SOIL  SURVEY  OF  THE  MIDDLE  GILA  VALLEY  AREA, 

ARIZOKA. 

By  E.  C.  ECKMANN,  In  Charge;  MARK  BALDWIN  and  E.  J.  CARPENTER— 
Area  Inspected  by  MACY  H.  LAPHAM. 

DESCRIPTION    OF   THE   AREA. 

The  Middle  Gila  Valley  area  is  situated  in  the  south-central  part 
of  Arizona,  mainly  in  Pinal  County,  only  2  s(|uare  miles  being  in 
Maricopa  County.  It  lies  in  a  region  of  isolated  or  discontinuous, 
barren,  rocky  peaks  and  ranges,  mainly  of  eruptive  and  crystalline 
formations,  which  rise  from  sloping  or  nearly  level  desert  plains. 
This  part  of  the  State  is  recognized  physiographically  as  the  Desert 
region,  in  contrast  to  the  much  higher  lying  Plateau  region  of  sedi- 
mentary rocks  occupying  the  northern  and  northeastern  parts  of  the 
State.  As  the  title  implies,  the  survey 
includes  the  middle  valley  of  the  Gila 
River,  which  presents  a  contrast  to  both 
the  upper  valley,  in  the  eastern  part  of 
the  State,  and  the  lower  desert  valley  above 
the  confluence  of  the  Gila  Eiver  with  the 
Colorado. 

The  area  surveyed  is  irregular  in  out- 
line, and  roughly  Y-shaped.  Beginning  at 
the  mouth  of  the  Gila  River  Canyon,  about 
6  miles  northeast  of  Florence,  it  spreads 
out  westward  and  southwestward  as  a  fan- 
shaped  area,  which  is  soon  divided  into 
two  arms  by  the  Sacaton  Mountains, 
which  it  practically  surrounds  on  the 
north,  east,  and  south.  The  northern  arm, 
lying  between  the  Sacaton  i\lountains  on  the  south  and  the  Santan 
Mountains  on  the  northeast,  extends  westward  to  Pima  Butte.  It 
includes  the  alhmal  bottoms  of  the  Gila  River,  with  parts  of  the 
adjacent  higher  lying  plains.  The  southern  arm  is  confined  to  a  tier 
of  townships  extending  westward  from  Picocho  Reservoir  in  town- 
ships 5  and  6  south  to  the  middle  of  range  5  east.  Small  parts  of  the 
adjoining  townslni)s  to  the  south  are  also  included.  The  area  in- 
cludes the  Sacaton,  Casa  Blanca,  Agency,  and  Blackwater  units,  and 
parts  of  the  Casa  Grande  and  Florence  units,  of  the  Gila  River  irri- 


FiG.  1. — Sketch  map  showing 
location  of  the  Middle  Gila 
Valley  area,   Arizona. 


6  FIELD  OPERATIONS   OF  THE   BUREAU   OF  SOILS,  lOl*?. 

gation  project  of  the  Office  of  Indian  Affairs.  The  Casa  Grande 
National  Monument  and  j^art  of  the  Gila  Eiver  Indian  Eeservation 
also  are  within  the  survey.  The  total  extent  of  the  area  is  352  square 
miles,  or  225,280  acres. 

The  area  is  made  up  almost  entirely  of  river  bottoms  or  smooth, 
nearly  level  plains,  the  adjoining  mountains  having  been  practically 
excluded,  except  for  several  small  hills  or  buttes.  The  most  promi- 
nent of  these  are  Twin  Butte,  Granite  Ivnob,  part  of  Cholla  Moun- 
tain, and  part  of  the  eastern  slope  of  Pima  Butte.  The  slopes  of  the 
included  hills  are  stony  and  steej). 

Elevations  within  the  area  range  from  about  1,150  to  1,525  feet 
above  sea  level.  Casa  Grande  has  an  elevation  of  1,396  feet;  Casa 
Grande  Ruins  (Casa  Grande  National  Monument),  1,422  feet; 
Florence,  1,493  feet;  and  S'acaton,  1,280  feet. 

The  Gila  River,  which  crosses  the  area  from  east  to  west,  is  the  sec- 
ond largest  stream  in  Arizona.  The  lands  lying  along  this  stream 
are  directly  drained  by  it,  but  the  greater  part  of  the  area  is  drained 
directly  by  McClellan  Wash,  which  reaches  the  Gila  River  within 
the  area.  Santa  Cruz  Wash  carries  the  drainage  from  the  southern 
part  of  the  area,  around  Casa  Grande,  and  enters  the  Gila  River  a 
short  distance  west  of  the  area.  The  McClellan  and  Santa  Cruz 
Washes  are  not  everywhere  well  defined,  and  they  are  inadequate  to 
drain  a  number  of  large  flat  areas.  The  Gila  River  has  a  channel 
varying  in  width  from  less  than  one-fourth  mile  to  a  mile  or  more. 
The  banks  of  this  stream  are  generally  poorly  defined  and  unstable. 
Shifting  of  the  channels  and  cutting  of  the  banks  take  place  at  each 
overflow,  and  the  process  is  increasingly  destructive  as  the  stream- 
bottoms  are  used  more  extensively  for  agriculture.  The  stream  has 
an  average  gradient  of  about  10  feet  per  mile  through  the  area. 

The  McClellan  and  Santa  Cruz  Washes  are  the  continuation  of  the 
drainage  of  the  Santa  Cruz  River,  which  ceases  to  maintain  a  definite 
channel  below  a  point  in  the  southern  part  of  Pinal  County,  its 
waters  spreading  oa  er  the  level  plain  or  flowing  slowly  down  the 
numerous  shallow  washes  between  Picocho  Reservoir  and  Casa 
Grande.  The  lands  along  the  McClellan  and  Santa  Cruz  Washes 
are  subject  to  overflow  from  flood  waters  that  come  from  the  region 
of  Tucson,  southeast  of  the  area  surveyed.  The  McClellan  Wash 
has  a  fall  of  about  20  feet  in  its  course  from  the  Picocho  Reservoir 
to  its  confluence  with  the  Gila  River. 

The  retarded  drainage  of  the  southern  part  of  the  area  gives  rise 
to  many  shallow  lakes  or  playa  flats,  which  are  dry  except  during 
heavy  rains.  These  flats  are  dotted  with  and  bordered  by  shifting 
sand  dunes. 

In  1910  the  population  of  l^inal  County  was  9,045 — an  increase  of 
16  per  cent  over  that  reported  in  1900.     While  the  area  surveyed 


SOIL  SURVEY   OF   THE  MIDDLE  GILA  VALLEY,  ARIZONA.  7 

covers  only  about  350  square  miles  in  Pinal  County,  whose  total  ex- 
tent is  5,380  square  miles,  it  includes  by  far  the  most  thickly  settled 
part  of  the  county.  The  number  of  Indians  in  1910  on  that  part  of 
the  Gila  Eiver  Indian  Reservation  in  Pinal  County  was  2,970,  or 
about  one-third  the  total  population  of  the  county.  About  64  per 
cent  of  the  total  population  is  white.  There  are  a  few  Negroes, 
Chinese,  and  Japanese.  About  46  per  cent  of  the  population  consists 
of  native  white  j^ersons  and  18  per  cent  of  foreign-born  white  per- 
sons. Of  the  foreign  born,  people  from  Mexico  :k>rm  by  far  the 
largest  num])er,  the  Mexicans  numbering  1,360  in  1910. 

The  population  of  the  cities  and  towms  is  made  up  chiefly  of  white 
persons.  The  Indian  population  is  of  the  Pima  tribe  and  confined 
almost  entirely  to  the  reservation.  Most  of  the  younger  Indians  have 
had  some  education  in  the  schools  maintained  by  the  Government 
and  are  able  to  use  the  English  language.  The  Mexican  population 
speaks  Spanish. 

Cities  and  towns  in  the  Middle  Gila  Valley  area  are  few  and  small. 
Florence  and  Casa  Grande  are  the  only  incorporated  places.  Saca- 
ton,  an  Indian  village,  the  location  of  the  Indian  Agency  and  of  an 
experimental  station  maintained  by  the  United  States  Department 
of  Agriculture,  lies  within  the  area  covered  by  the  survey.  Black- 
water,  Casa  Blanca,  Santan,  and  Sweetwater  are  the  most  important 
of  the  Indian  villages  within  the  reservation.  Florence,  with  a  popu- 
lation of  807,  is  the  largest  town  in  the  area  and  the  county  seat  of 
Pinal  County.  Casa  Grande  is  the  principal  railroad  and  shipping 
point  of  the  area.  Sacate  is  a  station  on  the  Arizona  Eastern  Rail- 
road, in  the  western  part  of  the  area. 

Three  railroad  lines  touch  the  area,  but  none  traverse  it  for  any 
distance.  The  Southern  Pacific  Railroad  cuts  across  the  extreme 
southwestern  part,  passing  through  Casa  Grande.  The  Arizona 
Eastern  Railroad  crosses  the  extreme  western  portion.  Florence  has 
access  to  a  branch  of  the  latter  railroad  which  follows  the  north 
bank  of  the  Gila  River  in  this  part  of  the  area.  The  town  is  on  the 
south  side  of  the  stream,  and  during  flood  periods  shipping  from  this 
point  is  sometimes  delayed  and  frequently  hazardous. 

Some  work  has  been  done  on  public  roads  in  this  area,  but  large 
tracts  are  still  without  roads.  During  dry  weather  most  of  the  roads 
are  readily  passable,  but  in  the  rainy  season  travel  is  frequently  very 
difficult.  There  are  no  bridges  across  the  Gila  River  at  the  present 
time  and  fording  is  often  impossible. 

The  products  raised  in  the  Middle  Gila  Valley  area  are  mostly 
of  nonperishable  nature  and  suitable  for  shipment  with  ordinary 
facilities.  In  many  places  farming  has  not  been  undertaken  or  is  not 
sufficiently  well  developed  to  meet  the  local  demands  for  agi'icultural 
products,  which  must  be  brought  from  outside  points. 


8  FIELD  OPERATIONS  OF   THE  BUREAU   OF  SOILS,  1917. 

CLIMATE. 

The  climate  in  this  region  is  characterized  by  a  long,  warm  grow- 
ing season;  a  shorter  cooler  season,  during  which  frosts  occur;  and 
a  scanty  supply  of  rain,  insufficient  to  insure  crops  without  irriga- 
tion. Two  so-called  wet  seasons  occur,  one  in  the  spring  and  one  in 
late  summer.  Except  for  the  hot  summer  months  the  climate  imyj  be 
said  to  be  exceptionally  pleasant  and  favorable  for  the  production  of 
crops. 

The  weather  records  kept  at  various  places  in  and  near  the  area 
are  incomplete.  In  some  instances  statistics  are  available  for  only 
a  short  period  of  years,  although  Casa  Grande  and  Maricopa  have 
kept  partial  records  since  1876.  The  data  nevertheless  indicate  in 
a  general  way  the  conditions  of  temperature  and  rainfall.  Phoenix 
is  representative  of  a  large  region  of  which  the  area  surveyed  is  a 
part.  The  mean  annual  precipitation  at  Phoenix  for  8  years,  from 
1896  to  1903,  inclusive,  was  6.8  inches.  The  average  number  of  days 
with  a  precipitation  of  0.01  inch  or  more  was  34  per  year.  The  pre- 
cipitation for  the  driest  year  was  3.7  inches  and  for  the  wettest  year 
12.8  inches.  At  Maricopa,  about  5  miles  southwest  of  the  area,  on 
the  open  desert  or  plain,  the  mean  annual  precipitation  for  a  period 
of  years  extending  from  1876  to  1907,  except  1878  and  1879,  was 
6.06  inches.  The  amount  for  the  driest  year  recorded  (1900)  was 
2.09  inches,  and  for  the  wettest  year  (1905),  13.51  inches.  The  table 
below,  compiled  from  records  of  th^  Weather  Bureau,  shows  the 
mean  annual,  seasonal,  and  monthly  rainfall  and  temperature,  the 
maximum  and  minimum  temperatures,  and  the  rainfall  for  the 
wettest  and  driest  years. 

Normal  monthhj,  seasonal,  and  annnal  temperature  and  preciiyitation  at 

Maricopa. 


Temperature. 

Precipitation. 

Month. 

Mean. 

Absolute 
maximum. 

■  Absolute 
minimum. 

Mean. 

Total 

amount 

for  the 

driest  vear. 

(1900). 

Total 
amount  for 
the  wet- 
test year. 
(1905.) 

50.9 
50.2 
54. 4 

"F. 
89 
88 
92 

"F. 
19 
S 
23 

Inches. 
0.82 
.59 
.62 

Inches. 
0.00 
.00 

T. 

Inches. 
0.85 

1.60 

2.70 

Winter 

51.  S 

92 

8 

2.03 

T. 

5.15 

60.4 
66.7 
74.3 

98 
104 

no 

25 
32 
39 

.52 
.20 
.09 

.20 
.40 
T. 

1.72 

1.71 

May 

T. 

Spring 

67. 1 

110 

25 

.SI 

.60 

3.43 

SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,  ARIZONA.  9 

Normal   monthly,   seasonal,   and  annual   tempero/ture,  etc. — Continued. 


Temperature. 

Precipitation. 

Month. 

Mean. 

Absolute 
maximum. 

Absolute 
minimum. 

Mean. 

Total 

amount 

for  the 

driest  year. 

(1900). 

Total 
amount  for 
the  wet- 
test year. 
(1905.) 

June 

T. 
85.9 
90.8 
90.5 

°F. 
126 
123 
119 

'F. 

49 
48 
65 

Inches. 
.08 
.78 
.99 

Inches. 
.00 
.24 

T. 

Inches. 
T 

July 

33 

August 

72 

Summer 

89.1 

126 

48 

1.85 

.24 

1  05 

September     

83.3 
70.3 
58.1 

117 
110 
101 

46 
30 

22 

.52 
.43 
.60 

T. 
T. 
1.25 

41 

October 

00 

November  

3  47 

Fall 

70.6 

117 

22 

1.55 

1.25 

3  88 

Year 

69.6 

126 

8 

6.24 

2.09 

13  51 

While  precipitation  may  occur  in  any  month  in  the  year,  two  wet 
seasons  are  the  general  rule.  The  spring  and  fall  months  are  usually 
warm  and  dry.  The  following  table  gives  the  best  data  available 
as  to  the  annual  precipitation  at  five  stations : 

Annual  precipitation  at  five  stations,  Middle  Gila  Valley  Area. 


Year. 

Casa 
Grande. 

Casa 
Grande 
Ruins. 

Mari- 
copa. 

Flor- 
ence. 

Saca- 
ton. 

liKhes. 

Year. 

Casa 
Grande. 

Casa 
Grande 
Ruins. 

Mari- 
copa. 

Flor- 
ence. 

Saca- 
ton. 

1876 

Inches. 

Inches. 

Inches. 
3.87 
6.27 

Inches. 
9.33 
5.35 
13.49 
12.02 
5.35 
12.14 

1898 

1899 

1900 

1901 

1902 

1903 

1904 

1905 

1906 

1907 

1908  . 

Inches. 

5.67 
3.20 
3.21 
5.04 
6.40 
4.65 
7.18 
19.52 
9.53 
5.70 

Inches. 

Inches. 
5.90 
4.95 
2.09 
4.69 
4.89 
4.72 
3.15 
13.51 
9.10 
7.57 

Inches. 

Inches. 

1877 

1878 

1879 

1880 

4.16 

1881 

1.58 
T. 
2.11 
9.26 
2.02 
5.02 
7.71 
3.65 
3.95 
10.70 
3.62 
8.75 
4.92 
5.82 
6.30 
6.43 
4.23 

1882 

0.38 
7.27 
11.96 
2.97 
6.12 
7.61 
3.99 
9.32 
8.63 
3.01 
6.05 
6.60 
6.57 
6.07 
6.69 
6.06 

1883 

1884 

1885     . . . 

1886 

1887 

1909 

7.26 
6.35 
9.83 
13.17 

7.85 
16.08 
12.11 

4.33 

8.87 
6.63 

8.89 

1888 

1910 

1911  

5.  .57 

5.45 

1889 

13.25 
13.8.5 
8.24 
9.95 
9.63 

1890 

1891 

1892 

1893 

1912 

1913 

1914 

1915 

9.56 
7.15 
9.87 

8.89 
5.03 

9.37 
10. 33 

8.96 
9.81 
12.41 
15. 32 
12.66 

12.12 
8.22 
16.75 
15.28 

1894 

1916 

10.39 

Annual 
mean  . 

6.28 

10. 38 

6.24 

10.40 

1896 

1897 

11.01 

Where  blanks  occur,  no  record  is  available. 
155289°— 20 2, 


10 


FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1017. 


The  precipitation  depends  somewhat  ii})on  the  h)cati()n  with  refer- 
ence to  mountains  and  canyons.  The  summer  rains  or  showers  are 
often  very  local,  and  in  the  form  of  heavy  downi)ours  accomi)anied 
by  lightning  and  thunder,  while  the  winter  rains  are  more  general 
and  fall  more  gently  over  a  longer  period  of  time.  The  summer 
rains  are  of  little  benefit  to  agriculture  directly  and  they  hinder  har- 
vesting and  fruit-drying  operations,  but  they  are  important  from 
the  standpoint  of  irrigation.  It  will  be  noticed  from  the  tables  that 
to  some  extent  wet  cycles  or  years  seem  to  be  followed  by  extremely 
dry  ones.  During  the  wet  cycles  there  is-  more  underground  water 
present  and  the  lands  are  farmed  for  the  time  being  by  irrigation 
with  pumped  water,  wdiich  during  dry  periods  is  scanty. 

The  following  table  shows  the  mean  annual  and  the  absolute  maxi- 
mum and  minimum  temperatures  for  several  stations  in  different 
parts  of  the  area : 

Average  annual   temperature  and   extremes  of  temperature   at   Casa   Grande 
Ruins,^  Florence,  and  Sacaton. 


Casa  GraiidP  Ruins. 

Florence. 

Sacaton. 

Mean. 

Max. 

Min. 

Mean. 

Max. 

.  Min. 

Mean. 

Max. 

Min. 

1916 

"F. 

"F. 

"F. 

"F. 
70.6 
69.0 
71.0 
68.9 

'F. 
113 
113 
112 
114 
115 

°F. 
20 
24 
27 
11 

"F. 
69.9 
68.9 
7014 
68.2 
67.6 

'F. 
114 
113 
114 
112 
113 

°F. 
15 

1915 

114 
112 
114 
113 
110 
113 

'  22 

1914 

1913 

1912 

69.9 
67.2 
66.  S 
68.4 
68.5 

23 

8 
18 
19 
16 

21 
9 
17 

1911 

1910 

1909 

71.2 

68.2 

115 
114 

22 
19 

71.3 

68.5 

117 
111 

17 
17 

'  Now  Casa  Grande  National  Monument. 

The  mean  annual  temperature  ns  recorded  at  Phoenix,  for  an  8- 
year  period  from  1896  to  1903,  inclusive,  was  70°.  The  absolute 
maximum  for  Maricopa  is  126°,  and  this  is  the  highest  temperature 
on  record  in  this  area  or  vicinity.  Temperatures  ranging  between 
110°  and  120°  are  recorded  yearly,  and  the  temperature  frequently 
remains  above  100°  for  periods  of  several  days  or  several  Aveeks  dur- 
ing the  summer.  During  the  early  summer  the  nights  are  cool,  but 
the  high  relative  humidity  accompanying  the  extremes  in  tempera- 
ture during  the  rainy  season  of  the  middle  and  late  summer  makes 
this  part  of  the  year  uncomfortable.  The  dry  part  of  the  year  is 
one  of  ^remarkably  low  relative  humidity,  xllthough  the  tempera- 
tures during  the  greater  part  of  the  year  are  moderate,  during  the 
winter  and  spring  low  extremes  of  temperature  for  this  part  of  the 
United  States  are  recorded.     For  instance,  absolute  mininuun  re- 


SOIL  SURVF.Y   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  11 

corded  at  the  Maricopa  station  is  8^  F.,  though  temperatures  as  low- 
as  25°  are  unusual,  and  even  crops  sensitive  to  cold  can  be  success- 
fully grown. 

The  prevailing  wind  direction  is  from  the  west.  Hot,  drying  winds 
are  frequent  during  the  summer  months.  Snow  very  seldom  falls, 
and  hail  is  of  local  occurrence  and  unimportant. 

The  growing  season  for  the  more  hardy  crops  extends  throughout 
the  year,  but  frosts  occur  during  December,  January,  and  February. 
The  average  date  of  the  last  killing  frost  in  the  spring  is  about 
March  7,  while  that  of  the  earliest  in  the  fall  is  about  November  27. 
The  latest  killing  frost  recorded  in  the  spring  at  the  Maricopa  sta- 
tion occurred  April  4,  while  the  earliest  in  the  fall  was  recorded  by 
the  same  station  on  October  22. 

AGRICULTURE. 

Agriculture  has  not  reached  a  very  high  state  of  development  in 
the  Middle  Gila  Valley  area,  although  there  is  abundant  evidence 
that  irrigation  fanning  was  carried  on  by  the  prehistoric  races  and 
Indians  for  centuries  preceding  settlement  by  the  whites.  The  lack 
of  game  and  wild  food  plants  on  the  arid  plains  and  treele&s  moun- 
tains forced  the  early  peoples  to  turn  their  attention  to  agriculture, 
and  the  river  bottoms  and  adjoining  higher  lands  that  could  easily 
be  irrigated  from  the  Gila  River  were  made  to  produce.  The  Pima 
Indians  have  no  traditions  of  the  prehistoric  race  or  races  that 
carried  on  agriculture  in  this  valley;,  but  the  ruins  of  their  dwellings 
and  canals  indicate  that  they  had  reached  a  rather  high  state  of 
culture.  Before  the  advent  of  the  white  man,  in  the  latter  part  of 
the  sixteenth  century,  American  Indians  were  irrigating  land  and 
producing  food  crops.  These  Indians  were  not  concerned  mainly 
Avith  warfare,  but  they  were  continually  called  upon  to  protect  their 
stores  of  grain  and  their  families  from  other  tribes.  The  small  farms 
along  the  Gila  Eiver  were  irrigated  with  the  silty  waters  of  the 
stream  by  means  of  small  ditches,  which  carried  the  flood  waters  a 
short  distance  to  the  cultivated  land.  Overflows  either  stimulated 
the  yields  or  destroyed  the  crops,  depending  upon  the  time  and 
manner  of  occurrence.  The  grain  was  harvested  in  the  crudest 
fashion  and  thrashed  with  a  flail  or  by  trampling  with  horses.  This 
method  of  harvesting  and  thrashing  grain  has  changed  little  among 
the  Indians,  their  hard-earth  thrashing  grounds  being  everywhere 
in  evidence.  The  farming  of  desert  land  lying  outside  the  river 
bottoms  was  not  looked  upon  with  much  favor  by  the  white  settlers, 
and  little  of  the  desert  slopes  is  cidtivated  to-day.  Extremely  h>ng 
droughts  and  low  average  rainfall  have  forced  settlers  to  abandon 
some  areas  formely  cultivated. 


12 


riELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 


Agriculture  is  confined  very  largely  to  that  part  of  the  Indian 
Reservation  occupying  the  river  bottoms,  to  scattered  ranches  in  the 
vicinity  of  Casa  (Irande  and  P'lorence,  and  to  a  few  scattered  farms 
in  various  other  parts  of  the  area.  The  construction  of  irrigation 
works  by  the  Government  for  the  Indians,  covering  lands  in  the 
river  bottom,  has  practically  assured  the  permanency  of  agriculture 
in  that  section. 

Farming  as  carried  on  by  the  settlers  and  squatters  on  the  desert, 
until  a  more  stable  supply  of  water  for  irrigation  is  obtained,  can 
hardly  be  considered  profitable.  The  canal  which  supplies  some  of 
these  farmers  carries  water  only  part  of  the  season,  or  may  even  be 
dry,  depending  upon  the  rainfall.  Others  irrigate  from  wells,- which 
seem  to  furnish  a  considerable  supply  of  water  in  wet  years,  but  can 
hardly  be  depended  upon  in  dry  seasons.  The  expense  of  application 
is  also  too  great  for  profitable  irrigation.  A  comprehensive  storage 
and  irrigation  system  is  necessary  before  the  barren  desert  plains  will 
be  turned  into  permanently  producing  fields. 

The  present  type  of  agriculture  differs  little  from  that  of  past 
years.  It  consists  largely  in  the  production  of  cereals,  alfalfa,  and 
other  hay  and  forage  crops,  and  the  raising  of  cattle  and  horses. 
Egyptian  cotton  is  groAvn  on  a  small  acreage.  Vegetables  are  grown, 
and  some  shipments  are  made  from  the  area,  but  most  of  the  produce 
is  used  locally,  as  the  demand  for  truck  and  garden  crops  far  ex- 
ceeds the  supply.  Small  quantities  of  tree  fruits,  mainly  peaches 
and  nectarines,  apples,  quinces,  apricots,  and  figs  are  produced.  A 
small  planting  of  the  date  palm  has  been  made  by  the  Department  of 
Agriculture  experiment  station. 

Statistics  of  agriculture  strictly  applicable  to  the  area  are  not 
available.  The  data  given  by  the  Federal  census  for  Pinal  County 
are,  however,  of  some  significance,  as  the  survey  covers  the  most 
important  agricultural  region  in  the  county. 

The  following  table  gives  data  for  the  three  principal  classes  of 
products  for  the  years  1899  and  1909 : 

Acreage  and  production  of  leadind  closscs  of  crops  and  value  of  ^live  stock, 

1S99  and  1909. 


Product. 


1899. 


Acreage. 


Production. 


1909. 


Acreage. 


Production. 


Cereals 

Tlay  and  forage 

liive  stock  sold  or  slaughtered. 


3,196 

4,633 

Numher. 


Bushela. 
79,330 
Tons. 

6,987 
Value. 
$134,895 


8,744 

4,232 

Number. 
8,162 


Buslicli. 
132,371 
Tons. 

6,709 
Valve. 
$148,905 


SOIL  SURVEY  OF   THE   MIDDLE  GILA  VALLEY,  ARIZONA.  13 

This  table  shows  a  very  considerable  increase  in  the  acreage  of 
cereals,  but  a  decrease  in  the  acreage  of  hay  and  forage  crops  during 
the  decade,  while  the  value  of  live  stock  sold  and  slaughtered  was 
materially  greater  at  the  end  than  at  the  beginning  of  the  period. 
It  is  certain  that  the  acreage  and  production  of  the  classes  of  crops 
stated  have  increased  since  the  last  census.  The  value  of  all  crops 
and  live-stock  products  in  1909  amounted  to  $406,228. 

Wheat,  barley,  and  corn  occupied  practically  the  entire  acreage  de- 
voted to  the  cereals  in  1909,  and  this  was  true  in  1899,  though  the  re- 
lations between  the  crops  were  ditferent.  In  1899  the  acreage  in 
barley  was  slightly  greater  than  the  acreage  in  wheat,  while  in  1909 
the  acreage  in  wheat  was  nearly  twice  that  in  barley. 

AVheat  in  1909  occupied  4,7()2  acres,  from  w  hich  the  production  was 
57,894  bushels,  an  average  yield  per  acre  of  about  12  bushels.  There 
were  2,552  acres  in  barley,  with  a  production  of  58,220  bushels,  or  an 
average  yield  of  22.8  bushels  per  acre,  and  1,275  acres  in  corn,  pro- 
ducing 13,999  bushels,  or  about  11  bushels  per  acre.  Corn  does  not 
yield  well  in  the  hot  valley  of  the  Gila  River.  It  is  grown  under  irri- 
gation. The  cereals  are  grown  mainly  for  home  consumption,  al- 
though wheat  and  barley  are  cash  crops  wdth  some  of  the  white 
farmers. 

From  these  returns  it  appears  that  the  average  yields  per  acre  of 
the  cereal  crops  are  low%  and  this  is  substantiated  by  facts  obtained 
during  the  survey.  The  low  average  yields  are  in  some  measure  due 
to  the  antiquated  methods  still  generally  used  by  the  Indians,  not- 
withstanding the  efforts  of  the  Government  to  educate  and  train 
them  in  better  farming  practices. 

Among  the  hay  and  forage  crops  of  1909,  grains  cut  green  for  hay 
occupied  2,721  acres,  or  more  than  half  the  total  acreage  in  such  crops. 
The  production  of  grain  hay  amounted  to  4,119  tons,  or  an  average 
yield  of  1|  tons  per  acre.  Alfalfa  was  the  next  important  hay  crop, 
the  acreage  being  776  acres,  the  production  1,569  tons,  and  the  yield 
per  acre  a  little  more  than  2  tons.  Millet  occupied  87  acres,  other 
tame  grasses  278  acres,  wild  grasses  250  acres,  and  coarse  forage  119 
acres.  Millet  yielded  about  3  tons  per  acre;  the  coarse  forage  be- 
tween 2  and  3  tons ;  and  the  other  crops  about  1  ton  per  acre. 

In  this  region,  where  stock  runs  on  the  range  throughout  the  year, 
the  production  of  hay  is  not  likely  to  be  considered  very  important, 
but  some  hay  is  made  by  most  farmers.  The  acreage  in  alfalfa, 
which  decreased  greatly  between  1899  and  1909,  has  increased  since 
the  latter  year,  and  the  area  in  this  crop  is  extending  annually,  both 
on  the  river-bottom  soils  and  on  the  desert  ranches.  This  legume  is 
one  of  the  most  valuable  crops  for  the  desert  farms,  where  water  for 
irrigation  can  be  obtained.  The  land  is  flooded  in  checks  and  when 
the  supply  of  water  is  sutiicient  an  irrigation  is  given  after  each  cut- 


14  FIELD   OPERATIONS   OF   THE   BUKIOAU   OF   SOILS,    l'.)17. 

tin<^,  of  which  there  may  be  as  many  as  seven.  Alfalfa  is  allowed 
to  occupy  the  land  for  many  years  without  reseeding.  Much  of  the 
land  in  cultivated  grasses  is  pastured  a  part  of  the  year,  Avhich  tends 
to  reduce  the  yield  of  hay.  The  forage  and  hay  crops  are  used 
largely  to  feed  the  work  stock  and  dairy  animals. 

According  to  the  census  neither  cotton  nor  the  sorghums  were 
grown  in  Pinal  County  in  1909.  Since  then,  mainly  as  the  result  of 
investigations  by  the  Bureau  of  Plant  Industry,  long-staple  Egyp- 
tian cotton  and  Egyptian  corn  and  milo  have  been  introduced. 

Long-staple  Egyptian  cotton  is  grown  extensively  in  adjacent 
parts  of  the  Salt  Eiver  Valley,  and  it  bids  fair  to  become  an  im- 
portant crop  in  this  area  when  facilities  for  irrigation  have  been  ex- 
tended. Several  strains  of  this  cotton,  which  seems  to  be  particu- 
larly adapted  to  the  soil  and  climate,  have  been  bred  to  a  high  stand- 
ard at  the  United  States  experiment  station  at  Sacaton.  Small  fields 
have  been  set  out  in  the  Middle  Gila  Valley  area,  both  white  and 
Indian  farmers  taking  up  culture  of  this  crop.  High  prices  during 
the  last  two  years  (1916  and  1917)  have  stimulated  the  interest  in 
cotton.  It  is  planted  after  all  danger  from  frost  is  past,  and  is  culti- 
vated and  irrigated  during  the  growing  season.  Much  hand  labor  is 
necessary  in  thinning,  chopping,  cultivating,  and  picldng.  Harvest- 
ing begins  in,  the  fall  and  may  continue  until  late  in  the  winter, 
which  usually  is  favorable  for  such  work. 

Egyptian  corn  and  milo  are  grown  more  extensively  each  year  and 
promise  to  become  important  crops,  as  they  are  well  adapted  to  the 
soil  and  climatic  conditions  and  can  be  grown  late  in  the  summer 
after  other  crops  are  disposed  of.  It  is  necessary  to  irrigate  the  land 
before  seeding.  Later  irrigations  depend  upon  the  season  and  rain- 
fall. These  grains,  which  make  excellent  stock  feed,  are  generally 
grown  by  the  white  farmers ;  the  Indians,  who  grow  grain  for  food, 
prefer  corn. 

Stock  raising  is  the  most  important  source  of  income  of  the  Pinal 
County  farmers.  Cattle  and  horses  are  kept  in  the  largest  num- 
bers, but  some  hogs,  sheep,  and  goats  are  raised.  Practically  all  of 
the  stock  subsists  on  the  desert  range  the  year  round,  seldom  being 
fed  at  any  time  of  the  year,  except  locally  during  severe  drought. 
Some  dairy  cattle  are  fed  and  pastured  on  alfalfa  the  year  round. 
Dairying  is  almost  entirely  in  the  hands  of  white  farmers,  and  is 
best  developed  in  the  vicinity  of  the  larger  towns.  The  income  from 
dairy  products  in  1909  was  $10,546.  Poultry  raising  is  carried  on  in 
conjunction  with  general  farm  operations,  the  value  of  poultry 
raised  in  1909  amounting  to  $15,306.  The  Indians  seem  more  adept 
in  the  raising  of  stock  than  in  farming.  The  (luality  of  the  cattle 
on  the  reservation  is  being  improved  through  the  agency  of  the 
Government. 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,  ARIZONA.  15 

Up-to-date  methods  ai'e  used  in  grain  farming  by  the  white  farm- 
ers, but  the  Indian  is  slow  to  adopt  modern  methods  and  the  use 
of  machinery.  Plowing  for  gi-ain  is  usually  done  in  the  fall  and 
winter  months,  about  the  time  of  the  first  winter  rains  or  following 
an  irrigation,  after  which  the  crop  is  planted.  In  dry  seasons  the 
crop  is  irrigated  a  number  of  times,  but  irrigation  may  be  entirely 
dispensed  with  in  years  of  greater  precipitation.  Not  much  grain 
is  produced  by  dry  farming.  Indians  continue  to  cut  their  small 
fields  of  grain  with  the  hand  sickle  and  thrash  the  crop  by  driving- 
horses  over  it  oil  a  hard  earth  floor,  later  separating  the  grain  from 
the  chaff  by  winnowing  or  throwing  it  into  the  air  on  a  windy  day. 

Little  or  no  fertilizer  except  barnyard  manure  is  used,  and  rota- 
tions are  not  practiced  to  any  extent.  The  application  of  very  silty 
irrigation  waters,  rich  in  organic  matter,  tends  to  maintain  or  in- 
crease the  productiveness  of  the  soils,  even  though  the  same  crop  be 
grown  for  a  period  of  years. 

Facilities  for  irrigation  and  alkali-free  soils  have  more  to  do  with 
the  present  distribution  of  crops  than  the  minor  differences  in  the 
texture  and  color  of  the  soil  or  the  source  and  character  of  the  soil 
material.  OrcMnarily  grain  does  best  on  the  rather  heavy,  silty  soils. 
Because  of  the  droughty  nature  and  low  organic  content  of  the  up- 
land soils,  the  present  agriculture  is  largely  confined  to  the  river 
bottoms.  The  farms  on  the  heavier,  low^er-lying  soil  types,  in  the 
river  bottom,  are  much  smaller  than  those  on  the  upland  soils,  prob- 
ably owing  to  the  fact  that  the  Indians,  occupying  much  of  the  river 
bottoms,  hold  only  small  parcels  of  irrigated  land.  Except  in  case 
of  the  Pinal  gravelly  sandy  loam,  topography  has  had  little  influence 
on  the  distribution  of  crops,  as  the  surface  of  all  the  other  types 
permits  of  irrigation  and  cultivation  without  great  difficulty. 

Farm  labor  is  supj^lied  principally  by  the  Pima  Indians.  Practi- 
cally all  the  Indians  own  small  tracts  of  land,  which  they  cultivate 
during  part  of  the  growing  season,  but  many  of  them  do  farm  labor 
in  the  vicinity.  In  and  around  Florence  and  C'asa  Grande  there  are 
many  Mexicans  who  perform  day  labor  on  the  ranches  in  that  sec- 
tion. The  wages  of  farm  labor  are  relatively  high  at  the  present 
time  (1917).  Mexicans  are  paid  $1.25  to  $1.50  a  day  and  board  for 
hand  labor,  while  men  who  handle  teams  receive  $1.50  to  $1.75  a  day 
and  board. 

In  1910  only  1.3  per  cent  of  the  total  area  of  Pinal  County  was  in 
farms.  The  total  number  of  farms  was  614,  and  the  average  size 
70.4  acres.  Of  this  43.5  per  cent,  or  30.6  acres,  was  improved.  The 
average  value  per  farm  of  all  farm  property  was  $3,757,  the  land 
making  up  51.4  per  cent  of  the  total  and  the  live  stock  37.2  per  cent. 
In  1910,  95  per  cent  of  the  farms  were  operated  by  owners,  a  small 


16  FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 

number  by  tenants,  and  a  very  few  by  managers.  This  hio^h  per- 
centage of  farms  operated  by  owners  is  due  mainly  to  the  large 
Indian  population. 

The  average  assessed  value  of  land  in  1910  was  $27.47  an  acre.  It 
is  very  difficult  to  estimate  the  average  value  of  farm  lands  at  the 
present  time,  as  no  sales  of  the  Indian  holdings  take  place,  and 
transfers  of  other  lands  have  been  few  in  recent  years.  Values  prob- 
ably range  from  a  few  dollars  to  $75  an  acre,  depending  upon  the 
means  of  irrigation  and  other  local  conditions. 

SOILS. 

The  soils  of  the  Middle  Gila  Valley  area  are  derived  from  a  variety 
of  rocks,  all  the  soils  except  those  identified  with  the  several  small 
buttes  and  parts  of  the  adjacent  mountains  having  been  transported 
and  laid  down  by  water.  The  predominating  rocks  in  the  mountains 
and  buttes  are  granite,  mica  schist,  and  other  crystallines.  Igneous 
rocks  of  low  quartz  content  and  of  basic  character  occur  on  some  of 
the  buttes,  and  have  entered  into  the  formation  of  the  soils  to  a 
small  extent.  In  the  western  and  southern  parts  of  the  area  small 
fragments  and  bowlders  of  igneous  rocks  have  been  washed  down 
over  the  desert  plains  by  torrents. 

The  soils  may  be  classed  in  three  main  groups — namely,  residual 
soils,  or  those  derived  in  place  through  the  weathering  and  distin- 
tegration  of  consolidated  rocks;  old  valley-filling  or  desert  soils, 
Avhich  are  derived  from  the  weathering  and  other  modification  of 
old  unconsolidated,  water-laid  material;  and  recent  alluvial  or 
stream  bottom  soils,  consisting  of  comparativel}^  recent  alluvial  prod- 
ucts which  have  undergone  no  important  changes  by  weathering  or 
internal  modification  subsequent  to.  deposition.  Another  main 
group — namely,  wind-laid  soils — is  represented,  but  is  not  of  suffi- 
cient extent  in  this  survey  to  warrant  separate  grouping,  and  it  is 
included  with  the  old  valley-filling  soils. 

The  main  groups  of  soils  are  divided  into  series  in  which  the 
soils  are  similar  in  color,  origin,  mode  of  formation,  subsoil  condi- 
tions, and  other  essential  features  except  texture.  The  series  are 
divided  into  types,  the  latter  being  determined  by  the  proportions 
of  sand,  silt,  and  clay  present  in  any  particular  case.  The  soil  type 
is  the  unit  of  mapping. 

Following  this  system  of  classification,  five  series  of  soils,  each 
represented  by  one  or  more  types,  are  recognized  in  this  survey. 
In  addition,  two  miscellaneous,  nonagricultural  soils  are  shown  on 
the  map — viz.  Rough  stony  land  and  Riverwash. 

Residual  soils. — The  residual  soils  in  the  Middle  (rila  Valley  area 
are  of  little  importance.     They  are  represented  only  by  Rough  stony 


Report  of  Bureau  of  Soils,  U.  S.  Dept.  of  Agriculture,  1917. 


Plate  I. 


4||e;«-*2 


Fig.  I. — View  Overlooking  Desert  Soils  Grouped  in  the  Mohave  Series. 

The  surface  is  smooth  and  gently  slopmg.    The  vegetation  is  typical  of  the  soils  of  this  series. 


Fig.  2. — Alfalfa   on    Mohave   Sandy  Loam,  Near   Casa   Grande. 

The  crop  has  been  cut  recently.    The  horizontal  ridges  are  irrigation  checks. 


Report  of  Bureau  of  Soils,  U.  S.  Dept.  of  Agriculture,  1917. 


Plate  II. 


Fig.  I. — View  in  Gila  River  Bottoms  Near  Florence. 

This  shows  the  smooth,  level  topography  of  the  Gila  silty  clay  loam.    The  field  in  the  foreground  is 

in  grain  stubble. 


Fig.  2. — Alfalfa  on  the  Gila  Silty  Clay  Loam,  Near  Florence. 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  17 

land   and   are   confined   to   the   small   rocky    buttes   and   mountain 
slopes. 

Old  vaUey-flUng  soils. — The  soils  of  the  old  valley-filling  province 
occupy  about  75  per  cent  of  the  area.  They  are  derived  from 
weathered  and  otherwise  modified,  relatively  old,  water-laid,  un- 
consolidated deposits,  which  oricrinally  had  their  source  in  a  variety 
of  formations  in  which  granites  and  related  rocks  seem  to  have 
predominated.  The  color  of  the  surface  soils  ranges  from  brown 
to  reddish  brown  or  red.  Oxidation  is  well  advanced  and  the  soils 
are  characteristically  low  in  organic  matter.  An  abundant  supply 
of  lime  is  present.  Heavier,  more  compact  subsoils  occur  in  places, 
and  frequently  a  greatly  compacted,  or  in  some  cases  cemented,  layer 
lies  within  a  few  inches  of  the  surface.  These  soils  cover  practically 
the  whole  of  the  area  except  the  valley  of  the  Gila  River.  The  sur- 
face is  smooth  and  comparatively  flat  or  gently  sloping.  The  soils 
have  a  moderate  elevation,  and  in  places  are  eroded.  Drainage  is 
good  over  most  of  this  area.  Three  series  of  soils  are  recognized — 
the  Pinal,  Mohave,  and  McClellan. 

The  soils  of  the  Pinal  series  are  pale  red  or  grayish  red  to  light 
reddish  brown  in  color,  and  predominantly  gravelly  or  stony.  Ce- 
mented, calcareous,  gravelly  hardpan  or  "caliche"  layers  are  prom- 
inently developed.  The  surface  is  gently  rolling  and  dissected  and 
drainage  is  good.  The  Pinal  series  is  inextensive  in  this  area  and 
unimportant  agriculturally.  Only  one  type,  the  Pinal  gravelly 
sandy  loam,  occurs  in  the  survey. 

The  soils  of  the  Mohave  series  have  a  range  in  color  from  light 
reddish  brown  to  dull  red  or  dull  reddish  brown.  They  are  usually 
underlain  by  grayish  or  pinkish-gray  very  compact  subsoils,  fre- 
quently containing  irregular,  partially  cemented  seams  or  layers, 
with  an  approach  to  a  dense,  cemented  "  caliche  "  or  hardpan.  The 
soils  are  low  in  organic  matter  and  high  in  lime.  They  generally 
kave  a  smooth  and  gently  sloping  surface  (see  PI.  I,  fig.  1),  which 
is  little  affected  by  erosion.  Surface  drainage  is  usually  well  estab- 
lished, but  the  subdrainage  is  restricted  and  some  areas  are  affected 
by  alkali  salts.  Two  types  of  this  series  are  mapped,  the  Mohave 
sandy  loam  and  fine  sandy  loam. 

The  McClellan  soils  are  browner  than  those  of  the  two  series  just 
described.  The  surface  soils  are  low  in  organic  matter,  high  in  lime, 
and  underlain  by  a  very  compact,  grayish,  calcareous  subsoil,  which 
retards  the  movement  of  moisture  and  limits  root  development.  The 
clay-loam  member  of  the  series  is  usually  very  low,  flat,  and  poorly 
drained,  while  the  loam  has  a  gently  sloping  surface  and  much 
better  drainage.  Part  of  the  series  is  affected  by  the  accumulation 
of  alkali  salts. 

155289°— 20 3 


18  FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 

Recent -alluvial  soils. — The  recent-alluvial  soils  of  this  area,  while 
not  the  most  extensive,  are  the  most  important  agriculturally.  They 
have  been  made  to  produce  crops  since  prehistoric  times.  They  are 
confined  to  the  Gila  River  bottoms  and  consist  of  recent  sedimentary 
materials  laid  down  by  this  stream.  As  distinguished  from  the  old 
valley-filling  soils,  they  are  naturally  friable  and  lack  a  compacted 
and  cemented  or  altered  subsoil.  They  are  much  higher  in  organic 
matter  than  the  old  valley-filling  types.  The  soil  profile  represents 
the  various  coarser  or  finer  strata  laid  down  by  the  stream  under 
different  conditions  of  velocity,  volume,  and  load  of  suspended  ma- 
terial. The  surface  is  generally  level  and  smooth,  and  the  soils  are 
in  places  poorly  drained  and  affected  with  alkali  salts.  They  are 
also  subject  to  overflows.  Two  series  are  included  under  this  soil 
province — the  Gila  and  the  Pima. 

The  Gila  series  consists  of  brown  soils,  ranging  from  rather  light 
grayish  brown  to  rather  dark  brown  in  color,  frequently  with  a 
slight  reddish  or  chocolate  tint.  The  subsoils  are  generally  similar 
in  color  and  texture,  but  they  may  consist  of  variably  textured,  alter- 
nating strata.  They  are  free  from  any  consistent  compact  or  hard- 
panlike  layers.  There  is  a  rather  high  percentage  of  organic  mat- 
ter in  the  surface  soil,  and  both  surface  soil  and  subsoil  are  calcareous. 
In  many  places  the  content  of  mica  is  large.  The  surface  of  the 
Gila  soils  is  usually  smooth  and  level  or  v^ry  gently  sloping,  and 
drainage  is  only  fairly  good.  Alkali  salts  are  sometimes  present  in 
excessive  quantities.  The  soils  are  subject  to  periodic  overflow  and 
have  a  high  water  table. 

The  Pima  soils  are  dark  brown  or  dark  grayish  brown,  with,  in 
many  places,  a  slight  reddish  or  rich  chocolate  brown  tint.  The  sub- 
soils are  of  similar  or  of  lighter  and  more  grayish  color,  particularly 
where  highly  calcareous.  Both  surface  soil  and  subsoil  are  cal- 
careous, effervescing  freely  with  dilute  acid.  The  subsoil  is  similar 
in  texture  to  the  surface  soil  or  consists  of  variably  textured  strata 
without  cementation  or  alteration  in  place  through  weathering. 
The  surface  is  generally  smooth  and  level.  The  soils  are  subject  to 
overflow,  and  at  times  are  poorly  drained.  In  some  places  the  Pima 
soils  contain  alkali  salts,  but  the  affected  areas  are  easily  reclaimed 
by  drainage  and  flooding. 

In  the  following  pages  of  this  report  the  various  soils  of  the  Mid- 
dle Gila  Valley  area  are  described  in  detail,  and  their  relation  to 
agriculture  discussed.  The  distribution  of  the  soils  is  shown  on  the 
map  accompanying  this  report,  and  the  table  below  gives  the  actual 
and  relative  extent  of  each : 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,  ARIZONA.  19 

Areas  of  different  soils. 


Sdl. 

Acres. 

Per  cent. 

Soil. 

Acres. 

Percent. 

Mf^lnllan  Jnam 

60,096 

1 

14,208 
6,464 
5,056 
4,608 

1,728 

6.3 

Shallow  phase            

5,568              30.6 
3  264 

Pima  clay              

2.9 

Siltypfea.se 

Gila  fine  sand        

2.2 

Mohave  sandy  loam 

40,384 
37, 824 

17.8 

16.8 

13.4 

7.2 

Pinal  gravelly  sandy  loam  . 
Rough  stony  land 

2.0 

0.8 

Total            

Mohave  f;no  sandy  loam . .              l.i- 836 

225,280 

PINAL.  GRAVELLY    SANDY    LOAM. 


The  Pinal  gravelly  sandy  loam  is  a  grayish-red  to  light  reddish 
broAvn  calcareous  sandy  loam,  carrying  a  large  quantity  of  rounded 
and  subangular  gravel,  as  well  as  bowlders  and  stones.  The  stony 
surface  material  usually  extends  to  a  depth  of  6  to  10  inches,  where 
a  gray,  calcareous  hardpan  or  "  caliche  "  is  encountered.  The  soil  is 
of  rather  loose,  friable  structure,  owing  to  the  large  content  of  coarse 
material.  It  is  high  in  lime  but  low  in  organic  matter.  The  hard- 
pan  is  a  firmly  cemented,  gravelly  layer  or  series  of  layers,  varying 
in  thickness  from  12  to  36  inches  or  more.  The  subsoil  consists  of  a 
grayish  or  grayish-brown,  calcareous,  compacted  mass  of  gravel  and 
bowlders  in  a  matrix  of  material  finer  than  that  in  the  surface  soil. 
It  extends  in  many  places  to  a  depth  of  6  feet  or  more,  but  locally  is 
underlain  at  varying  depths  by  compact,  heavy  and  more  silty  mate- 
rial, free  from  gravel.  A  deep,  gravelly  substratum  underlies  the 
type.     This  also  is  calcareous. 

The  Pinal  gravelly  sandy  loam  occurs  in  areas  of  varying  size,  the 
largest  lying  west  of  Florence  along  the  Blackwater  and  Florence 
Road.  For  several  miles  this  area,  occupying  a  more  or  less  eroded 
terrace,  forms  the  southern  boundary  of  the  Gila  Valley.  Areas  of 
similar  characteristics  skirt  the  valley  north  of  the  river,  but  only  a 
small  part  is  included  in  this  survey.  Three  small  areas  are  mapped 
east  of  Casa  Blanca  and  one  southeast  of  Casa  Grande.  The  latter 
is  of  particularly  stony  character. 

The  surface  of  the  type  is  somewhat  undulating  and  eroded  and 
not  well  adapted  to  irrigation.  The  gravelly,  stony  nature  of  the 
soil  and  the  nearness  of  the  "  caliche  "  to  the  surface  render  the  type 
difficult  to  handle.  The  surface  run-off  is  rapid  and  the  soil  is  not 
retentive  of  moisture. 

The  Pinal  gravelly  sand}'  loam  is  at  present  used  solely  for  pasture. 
It  supports  only  a  sparse  growth  of  grasses  or  creosote  bush,  and  its 
pasturage  value  is  low. 


20  FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 


MOHAVE   SANDY   LOAir. 


The  Mohave  sandy  loam  consists  of  a  pale-red  to  reddish-brown, 
friable,  calcareous,  light-textured  sandy  loam,  about  1*2  or  14  inches 
deep,  underlain  by  a  calcareous,  light  reddish  brown  or  pinkish-gray 
compact  sandy  loam  or  loam.  The  surface  soil  is  open  in  structure, 
and,  containing  little  organic  matter,  has  little  power  to  retain 
moisture.  Considerable  quantities  of  coarse  sand  and  fine  gravel  and 
grit  are  normally  present.  Coarse  angular  gravel  occurs  in  the  soil 
where  it  adjoins  the  Pinal  gravelly  sandy  loam  or  other  stony  types. 
The  subsoil,  while  calcareous  and  compact,  is  not  advanced  in 
cementation  to  the  stage  of  a  true  hardpan.  In  most  places  a  water- 
bearing stratum  of  rounded  gravel  underlies  the  t3^pe  at  a  depth  of 
25  to  35  feet  or  more,  and  it  is  from  this  stratum  that  water  for  irri- 
gation is  usually  obtained. 

Small  areas  of  a  sandy  variation  are  included  in  this  type,  and  it 
may  include  some  areas  having  the  texture  of  a  sand.  In  the  sandier 
areas  the  soil  is  usually  deeper  and  more  open  in  structure,  and  the 
subsoil  carries  some  fine  angular  gravel. 

The  Mohave  sandy  loam  is  an  extensive  and  important  soil.  It  is 
mapped  in  all  parts  of  the  area,  but  the  largest  bodies  occur  in  the 
eastern  and  southern  parts.  Many  of  the  soil  areas  are  elongated  and 
roughly  parallel.  They  may  extend  along  drainage  courses,  or 
bound  large  flat  areas.  Some  are  small,  isolated  areas  of  sandier 
material,  which  have  been  modified  by  wind  action  and  may  locally 
have  a  veneer  of  wind-laid  material.  The  soil  boundaries  in  most 
cases  are  definite  and  in  many  cases  sharp. 

The  surface  of  the  type  is  generally  smooth  and  well  suited  to  irri- 
gation and  agriculture,  but  some  of  the  smaller,  sandv  areas  are 
marked  by  small  hillocks  and  are  difficult  to  handle.  Leveling  is 
necessary  to  j^repare  much  of  the  type  for  irrigation. 

This  soil  usually  lies  slightly  higher  than  the  surrounding  or  adja- 
cent types,  and  drainage  is  toward  the  latter.  It  is  well  drained 
and  is  seldom  affected  by  alkali,  which  occurs  only  along  marginal 
areas. 

The  greater  part  of  this  type  still  supports  the  native  vegetation 
of  creosote  bush  and  varieties  of  cacti  or  other  desert  plants.  Small 
areas  are  irrigated  and  farmed,  alfalfa  being  the  principal  crop. 
(PI.  I,  fig.  2.)  Where  sufficient  water  is  available  the  yields  are 
good,  but  all  crops  require  irrigation.  Some  grain  is  produced,  but 
the  yields  are  often  poor.  Kafir,  milo,  and  truck  crops  are  grown 
locally,  and  their  acreage  is  being  extended.  A  small  acreage  is 
devoted  to  peaches,  apricots,  and  figs.  Egyptian  cotton  is  not  grown 
on  the  type  in  this  area,  but  it  is  produced  on  similar  or  identical 
soils  outside  the  survey.  The  seed  farm  of  the  Indian  Agency  near 
Sacaton  is  located  on  this  type  of  soil. 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  21 

The  value  of  raw  land  of  the  Mohave  sandy  loam  ranges  between 
$12  and  $75  an  acre,  depending  upon  the  location  and  water  supply. 

The  addition  of  organic  matter  to  this  soil  would  improve  its 
physical  condition.  Where  manures  and  green  crops  have  been 
plowed  under,  or  where  the  silty  irrigation  waters  of  the  Oila  River, 
rich  in  organic  matter,  have  inundated  the  surface,  tlie  improvement 
is  noticeable. 

MOHAVE  FINE  SANDY   LOAM. 

The  surface  soil  of  the  Mohave  fine  sandy  loam  is  a  pronounced 
reddish-brown  or  pale- red  to  grayish-red,  rather  coarse  and  gritty, 
calcareous  fine  sandy  loam,  6  to  10  inches  deep.  The  subsoil  is  a 
very  compact,  light-red  or  brownish-red  or  grayish-red  calcareous 
fine  sandy  loam,  or  loam  in  which  occur  lenses  or  layers  of  partly 
cemented  material.  Under  irrigation  the  hard  layers  soften  some- 
what, but  even  the  uncemented  subsoil  is  so  compact  that  the  move- 
ment of  moisture  and  the  penetration  of  plant  roots  are  hindered. 
The  same  condition  decreases  the  water-holding  capacity  of  the  soil. 
A  gravelly  substratum  underlies  the  type  at  considerable  depth. 

This  type  is  very  uniform  over  large  areas,  but  in  places  the  soil 
has  been  modified  by  winds,  the  surface  soil  in  such  places  being 
deeper  and  more  open  and  friable  than  typical.  The  surface  of  the 
greater  part  of  the  type  is  smooth  and  favorable  to  cultivation  and 
irrigation. 

The  larger  areas  have  sufficient  slope  to  insure  good  drainage,  and 
as  a  result  of  the  structure  of  the  subsoil  most  of  the  precipitation 
is  lost  as  run-oiF.  Some  lower  lying  areas  of  the  type  are  affected  by 
accumulations  of  alkali.  The  narrow  ridges  of  this  type,  which 
border  flats  occupied  by  heavier  soils  need  leveling  before  they  can 
be  cultivated. 

The  Mohave  fine  sandy  loam  is  an  extensive  soil.  Most  of  it  occurs 
in  large  bodies  north  of  Casa  Grande  and  along  McClellan  Wash. 
Smaller  areas  are  mapped  to  the  southeast  of  Casa  Grande,  northwest 
of  Santan,  and  north  and  northwest  of  Tw^in  Butte.  One  small  area 
occurs  west  of  Blackwater  and  another  west  of  Casa  Blanca.  The 
native  vegetation  consists  of  a  growth  of  desert  sage,  creosote  bush, 
and  several  varieties  of  cacti.  In  areas  where  alkali  salts  have  ac- 
cumulated "seep  weed"  is  a  common  plant. 

Little  of  the  type  is  under  cultivation.  Several  farms  are  pro- 
ducing alfalfa,  but  no  data  as  to  yields  are  obtainable.  The  non- 
saccharine  sorghums,  cotton,  and  truck  crops  can  be  produced  where 
the  soil  is  free  from  alkali  and  where  subsurface  conditions  are  fa- 
vorable. Peaches,  apricots,  and  figs  are  produced  locally.  The  type 
is  low  in  organic  matter  and  responds  to  applications  of  manure  or  to 
the  incorporation  of  green  manures.  Much  of  it  is  very  droughty, 
owing  to  the  shallow  soil  and  compact  structure  of  the  subsoil. 


22 


FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 


The  results  of  mechanical  analyses  of  samples  of  the  soil  and  sub- 
soil of  Mohave  fine  sandy  loam  are  shown  in  the  following  table : 

Mechanical  anaUjses  of  Mohave  fine  saoidij  loam. 


Number. 

Description. 

Fine 
gravel. 

Coarse  • 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  flue 
sand. 

Silt. 

Clay. 

510411 

Soil            

Per  cent. 
2.5 

Per  cent. 
9.4 
7.1 

Per  cent. 
5.1 
4.2 

Per  cent. 
34.1 
28.0 

Per  cent. 
30.0 
22.0 

Per  cent. 
16.7 
17.3 

Per  cent. 
2.4 

510412 

Subsoil 

2.0 

19.4 

M  CLELLAN    LOAM. 


The  surface  soil  of  the  McClellan  loam  typically  consists  of  a 
brown,  gritty,  light-textured  loam,  10  to  20  inches  in  depth.  It  has 
usually  a  slight  reddish  or  purplish  tint.  The  surface  soil  is  more 
compact  and  retains  moisture  better  than  the  Mohave  fine  sandy  loam 
and  sandy  loam,  but  it  lacks  organic  matter  and  has  a  tendency  to 
bake  upon  drying.  Some  fine  gravel  is  generally  present  on  the  sur- 
face and  coarser  material  occurs  along  the  small  washes  or  drainage 
ways.    The  soil  conttiins  much  lime. 

The  subsoil  is  a  compact,  highly  calcareous,  gritty  loam,  of  light 
grayish  brown  or  pinkish-gi'a}'  color.  In  places  it  is  weakly  cemented 
and  occasionally  the  deeper  subsoil  is  a  very  compact,  reddish,  or  red- 
dish-brown loam  or  clay  loam,  not  well  adapted  to  root  development. 
Where  it  has  been  subjected  to  a  high  water  table,  the  subsoil  is  often 
grayish  or  grayish  brown.  The  type  is  underlain  by  a  deep  gravelly 
substratum. 

The  McClellaa  loam  in  this  survey  is  subject  to  some  variations  in 
texture,  color,  and  depth.  In  several  places  south  of  Casa  Blanca 
small  areas  have  a  pronounced  reddish  brown  color  and  others  occu- 
pjang  slopes  have  a  somewhat  deeper  surface  soil  than  typical. 
Small  areas  of  lighter  or  slightly  heavier  texture  are  also  included. 
Much  of  the  type  in  the  western  part  of  the  survey  contains  alkali 
in  injurious  quantities. 

The  McClellan  loam  is  one  of  the  most  extensive  types  in  the  area. 
It  occurs  in  all  sections  except  the  Gila  River  flood  plain,  in  both 
large  and  small  bodies. 

The  type  represents  part  of  an  extensive  plain,  in  which  drainage 
ways  are  poorly  developed.  It  is  generally  level  or  gently  sloping, 
and  is  easily  handled,  such  surface  irregidarities  as  exist  being  of 
little  hindrance  to  irrigation  or  cultivation.  Parts  of  the  type  are 
well  drained,  but  in  general  surface  drainage  is  not  well  established, 
and  the  subdrainage  is  retarded  by  the  impervious  or  compact  sub- 
soil.   The  poorly  drained  areas  contain  more  or  less  alkali. 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  23 

The  type  is  used  largely  for  pasture  because  of  the  lack  of  water 
for  irrigation.  A  desert  growth  of  Atriplex  or  desert  sage,  mesquite, 
creosote  bush,  cacti,  and  seep  weed  forms  the  principal  vegetation. 
"Where  the  soil  is  free  from  alkali  and  can  be  irrigated,  alfalfa,  non- 
saccharine  or  grain  sorghums,  and  other  grains  are  produced.  Al- 
falfa and  the  sorghums  give  good  returns,  but  the  yields  of  other 
crops  are  only  fair.  Garden  truck,  melons,  peaches,  apricots,  and  figs 
are  grown  locally.  Egyptian  cotton  is  produced  on  this  type  outside 
the  area.  The  content  of  organic  matter  in  this  soil  is  low.  oxidation 
of  humus  being  rapid.  Liberal  applications  of  manure  or  the  turn- 
ing under  of  gi-een  crops  is  necessary  for  best  results. 

The  selling  value  of  land  of  this  type  varies  greatly,  depending 
upon  the  location  and  the  facilities  for  irrigation. 

McClellmi  loam,  shallow  pJiase. — The  shallow  phase  of  the  Mc- 
Clellan  loam  differs  from  the  typical  soil  chiefly  in  the  depth  of  the 
surface  soil.  The  soil  section  consists  of  (1)  a  layer  of  brown  loam 
or  fine  sandy  loam,  3  to  6  inches  deep,  and  (2)  a  layer  of  compact, 
reddish-brown  or  brown  loam  weakly  or  intermittently  cemented  and 
approaching  a  hardpan  in  general  characteristics.  Both  soil  and  sub- 
soil are  calcareous. 

The  principal  areas  of  this  phase  are  mapped  along  McClellan 
Wash  and  southwest  of  Casa  Blanca.  It  supports  in  general  a 
stunted  vegetation  of  sage,  seep  weed,  and  dwarf  cactus.  A  few 
barren  spots  occur.  The  soil  is  level  and  poorly  drained.  It  is  over- 
flowed frequently  from  the  McClellan  Wash,  and  occasionally  re- 
ceives seepage  from  the  higher  lying  types.  The  unfavorable  struc- 
lure  of  the  soil,  the  liability  to  overflow,  and  the  accumulations  of 
alkali  render  the  land  of  little  value  except  for  pasture,  and  none  of 
it  is  cultivated  at  present. 

McClellan  loam^  sUty  phase. — The  silty  phase  differs  from  the 
typical  McClellan  loam  in  having  a  larger  content  of  silt  in  the  upper 
foot  or  two.  and  in  having  larger  proportions  of  organic  matter.  The 
soil  consists  of  a  dark-brown  silty  loam  5  to  24  inches  deep,  and  the 
subsoil  of  material  like  that  of  the  typical  soil,  but  somewhat  more 
porous.  The  excess  of  silt  is  due  to  the  deposition  of  material  carried 
by  irrigation  or  overflow  waters.  The  soil  is  darker  than  the  typical 
McClellan  loam.    Parts  of  the  phase  are  spotted  with  alkali. 

This  soil  is  not  very  extensive.  The  principal  areas  are  situated 
several  miles  east  and  southeast  of  Casa  Grande,  and  southeast  of  the 
Casa  Grande  National  Monument.  Those  east  and  southeast  of  Casa 
Grande  are  elongated  and  form  shallow  drainage  channels.  The 
phase  lies  lower  than  the  adjacent  soils,  and  in  places  receives  run-off 
from  surrounding  areas.  The  drainage  is  nevertheless  good  over 
most  of  it. 


24  FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1^17, 

The  silty  phase  is  better  adapted  to  farming  than  the  typical  Mc- 
Clellan  loam  and  practically  all  of  it  is  cultivated,  being  devoted  to 
alfalfa,  grain,  and  the  sorghums. 

m'clei.lan  clay  loam. 

The  McClellan  clay  loam  consists  of  a  brown,  rather  smooth, 
sticky,  compact  clay  loam,  relatively  high  in  silt  from  3  to  12  inches 
deep.  The  soil  is  somewhat  darker  than  the  soils  of  the  Mohave 
series  and  the  red  color  is  much  less  pronounced,  though  a  reddish 
or  purplish  brown  tint  is  noticeable  in  most  of  the  ai'eas.  The  con- 
tent of  organic  matter  also  is  higher  than  in  the  Mohave  soils,  but 
nevertheless  the  type  bakes  and  hardens  upon  drying,  and  assumes  a 
dense,  impervious  structure  which  retards  percolation  and  absorp- 
tion of  water.  The  subsoil  is  a  light  reddish  brown  or  pinkish, 
stick}'  clay  loam,  which  becomes  more  compact  with  depth  and  is 
weakly  and  irregularly  cemented  in  places,  in  character  approaching 
a  hardpan.  Its  close  structure  renders  the  percolation  of  water  very 
slow  and  retards  root  development.  The  subsoil  usually  becomes 
lighter  colored  or  reddish  brown  at  a  depth  of  3  feet  or  more.  In 
some  places,  where  the  shallow,  silty  surface  material  has  been 
removed,  the  entire  soil  column  consists  of  the  impervious,  com- 
pacted subsoil  material.  A  substratum,  consisting  of  gravel  and 
bowlders,  lies  at  about  25  feet  below  the  surface.  Both  surface  soil 
and  subsoil,  but  particularly  the  latter,  contain  large  amounts  of 
lime. 

The  McClellan  cla}^  loam  is  a  very  extensive  soil,  occurring  prin- 
cipally in  the  southern,  western,  and  northwestern  parts  of  the 
survey.  Many  of  the  areas  are  large  "  playa  "  flats,  or  smooth  flat 
areas  of  puddled  soil,  barren  of  vegetation.  Others  occupj^  elongated, 
shalloM'  depressions  or  channels  which  may  carry  the  run-off  or  may 
hold  water  until  it  is  ren^oved  by  evaporation  and  percolation.  The 
elongated  areas  roughly  parallel  the  principal  drainage  ways. 

Areas  of  this  type  are  frequently  separated  from  each  other  by 
ridges  of  lighter  textured,  wind-blown  material,  and  the  flats  are 
usually  bordered  by  such  ridges.  In  general  the  areas  of  this  soil 
lie  near  the  principal  drainage  ways  in  the  desert  part  of  the  area. 

The  surface  is  uniformly  level  and  flat,  drainage  ways  being  very 
feebly  developed  except  in  the  case  of  the  larger  washes.  During 
periods  of  drought  these  flats  are  dry  and  the  soil  is  baked,  but 
during  the  rainy  season,  or  after  heavy  showers,  they  are  occupied 
by  shallow  lakes.  The  surface  material,  consisting  mainly  of  silt  and 
clay,  is  largely  the  result  of  deposition  from  the  turbid  drainage 
waters.  Alkali  salts  are  usually  present  in  greater  or  less  concentra- 
tions.    In  the  southern  part  of  the  survey  only  small  amounts  of 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA. 


25 


alkali  are  present,  but  injurioiis  quantities  occur  in  the  western  and 
northwestern  parts. 

While  much  of  the  McClellan  clay  loam  is  without  vegetation, 
parts  of  it  have  a  growth  of  mesquite,  sage,  and  dwarf  cactus.  The 
occasional  presence  of  standing  water,  followed  by  a  baked  condition 
of  the  soil,  renders  the  broad  fiats  occupied  by  this  type  unsuited  to 
the  native  plants  even  where  the  content  of  alkali  is  low.  The  bar- 
ren areas  are  known  locally  as  "  slicks." 

The  soil  is  used  to  some  extent  for  pasture.  Owing  to  the  generally 
poor  physical  condition  of  the  soil,  the  poor  drainage,  the  alkali 
accumulations,  and  the  cost  of  reclamation,  farming  has  not  been 
attempted  except  in  a  few  of  the  more  favorable  situations.  Grain 
is  the  principal  crop  grown.  Where  the  subsoil  conditions  are  better 
than  typical  and  the  soil  is  free  from  alkali,  good  yields  are  obtained 
under  irrigation,  but  the  selling  value  of  the  land  is  low. 

The  table  below  gives  the  results  of  mechanical  analyses  of  samples 
of  the  soil  and  subsoil  of  the  McClellan  clay  loam : 

Meclxnnkal  analyses  of  McClellan  clay  loam. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
Band. 

Silt. 

Clay. 

510417 

Soil 

Per  cent. 
0.3 
2.4 

Per  cent. 
2.0 
7.1 

Per  cent. 
1.4 
3.5 

Per  cent. 
10.8 
14.5 

Per  cent. 
18.2 
17.1 

Per  cent. 

42.8 
25.6 

Per  cent. 
24.6 

51041S 

Subsoil 

29  6 

GILA   FINE  SAND. 


The  Gila  fine  sand  consists  of  a  friable,  brown  fine  sand,  3  to  6  feet 
deep,  underlain  by  variably  textured  stratified  sediments.  The 
mellow,  open  soil  is  not  as  high  in  organic  matter  as  the  Gila  silty 
clay  loam,  but  it  is  moderately  well  supplied.  It  absorbs  moisture 
easily,  but  does  not  retain  it  as  well  as  the  silty  clay  loam.  The  soil 
is  micaceous  and  well  supplied  with  lime.  In  poorly  drained  areas 
the  subsoil  is  often  slightly  more  compact  and  lighter  colored  than 
the  surface  soil,  but  it  is  favorable  to  root  development  except  where 
waterlogged. 

In  local  areas  adjacent  to  the  Gila  River  the  soil  is  more  silty  than 
typical,  and  sometimes  a  light  fine  sandy  loam  in  texture,  while  along 
the  Little  Gila  it  contains  more  sand  and  fine  sand.  The  subsoil  is 
highly  calcareous.  Small  amounts  of  gravel  occur  locally  along  the 
streams.  Two  small  islands  in  the  Gila  River  are  clas.sed  Avith  the 
type,  although  the  soil  is  coarser  textured  than  typical.  The  channels 
of  the  Gila  and  Little  Gila  Rivers  are  occupied  by  material  similar 
to  this  soil,  but  owing  to  their  position  they  are  classed  with  River- 
wash. 


26 


FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   lf>17. 


The  (hla  fine  sand  is  not  extensive.  It  occurs  only  in  tlie  Gila 
River  bottoms  from  the  northeastern  end  of  the  area  westward  to 
l*.inia  Butte.  The  soil  is  developed  in  long;,  narrow  strips  along;  the 
channel  of  Gila  and  Little  Gila  Rivers. 

The  soil  is  well  drained  in  the  upper  3  or  4  feet,  and  in  places  to  a 
much  greater  depth,  but  much  of  it  has  a  high  water  table.  The 
texture  and  structure  of  the  soil  being  favorable  to  the  capilliary 
movement  of  the  water,  parts  of  the  type  contain  large  quantities  of 
alkali,  though  tlie  areas  periodically  overflowed  do  not  contain  in- 
jurious amounts. 

The  surface  is  generally  level,  but  not  always  smooth.  Overflows 
usually  leave  it  in  a  hummocky  or  slightly  eroded  condition,  and  con- 
siderable leveling  is  necessary  to  fit  the  land  for  irrigation. 

Wliere  alkali  is  absent  there  is  a  growth  of  cottonwood  and  willow. 
In  the  alkali  areas  such  plants  as  seep  weed,  mescjuite,  greasewood, 
and  pickleweed  flourish.  Alfalfa,  cotton,  nonsaccharine  sorghums, 
grains,  corn,  and  truck  and  root  crops  produce  good  yields  on  the 
well-drained  parts  of  the  type,  which  are  free  from  alkali.  Many 
kinds  of  tree  fruits,  the  date  palm,  vegetable  crops,  and  melons  are 
grown  at  tlie  experiment  station  at  Sacaton,  and  it  is  likely  that  some 
of  these  crops  will  be  more  extensively  grown  by  the  farmers. 
Manures  and  fertilizers  are  not  Avidely  used. 

The  results  of  mechanical  analyses  of  samples  of  the  soil  and  sul:)- 
soil  of  the  Gila  fine  sand  are  given  in  the  following  table : 

Mechanical  analyses  of  Gila  fine  sand. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt.           Claj-. 

510407. JL..   . 

Soil 

Per  cent. 
0.0 
.0 

Per  cent. 

0.8 

_  2 

Per  cent. 
0.5 
.1 

Per  cent. 
06.  6 
15.9 

Per  cent. 
20.0 
11.1 

Per  cent. 
8.6 

51.8 

Per  cent. 
2.8 

610408 

17.6 

GILA    SILTY    CLAY    LOAM. 


The  Gila  silty  clay  loam  is  a  smooth,  close-structured,  brown,  silty 
clay  loam,  the  color  in  places  having  a  slightly  reddish  or  choco- 
late-brown tint.  The  soil  usually  extends  to  a  depth  of  3  to  6  feet 
with  little  change,  except  that  below  a  depth  of  1  or  2  feet  the  color 
may  be  somewhat  lighter  and  the  structure  somewhat  more  compact. 
The  surface  soil  contains  a  relatively  large  proportion  of  organic 
matter  and  is  distinctly  micaceous.  The  soil  and  subsoil  material  is 
high  in  lime.  In  many  places  the  materials  forming  this  type  do  not 
appear  to  be  of  as  recent  deposition  as  those  giving  the  Gila  fine  sand, 
but  even  here  the  .subsoil  has  not  been  cemented  or  altered  by 
weathering. 


SOIL  SUEVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  27 

The  type  as  mapped  includes  some  variations.  While  the  color  of 
tlie  surface  soil  is  uniform  for  so  extensive  a  type,  some  areas  have  a 
darker  color,  owing  to  a  larger  admixture  of  organic  matter.  In  de- 
pressions the  soil  is  both  heavier  and  darker  than  the  typical  soil, 
and  on  some  narrow  ridges  it  is  coarser  and  lighter.  As  mapped 
some  material  of  silt-loam  texture  is  included.  AVhere.poor  drain- 
age exists  and  alkali  has  accumulated  the  subsoil  is  usually  lighter 
colored  and  more  compact  than  the  subsoil  in  other  parts  of  the  type. 
Harmful  concentrations  of  soluble  salts  occur  over  a  large  part  of 
the  type.  The  substratum  is  similar  to  the  subsoil  to  a  depth  of 
many  feet.    Below  this  are  l)eds  of  river  gravels. 

The  Gila  silty  clay  loam  is  an  extensive  and  important  soil  occu- 
pying the  greater  part  of  the  Gila  River  bottoms.  The  surface  is 
generally  level  and  moderately  smooth,  well  adapted  to  irrigation 
and  cultivation  (see  PI.  II,  fig.  1).  The  sandier  ridge  areas  require 
leveling  before  they  are  farmed.  Much  of  the  type  lies  on  a  second 
terrace  a  few  feet  above  the  normal  overflow  of  the  river.  On  the 
whole  it  is  not  thoroughh^  drained,  and  much  of  it  as  the  result  of 
seepage  has  a  high  water  table.  Capillary  movement  of  moisture  is 
rapid  and  much  of  the  type  is  damaged  by  alkali,  small  tracts  being 
barren  of  vegetation.  AYhile  not  often  overflowed  by  fl(^ods  in  the 
Gila  River  it  is  subject  to  overflow  from  other  sources.  Mesquite. 
greasewood,  seep  weed,  and  a  little  salt  grass  are  the  characteristic 
plants  in  the  vegetation. 

The  Indians  have  farmed  parts  of  the  Gila  silty  clay  loam  for 
many  years,  growing  wheat,  barley,  hay,  alfalfa,  corn,  sorghums, 
and,  recently,  cotton.  Truck  and  root  crops  are  grown  locally.  Be- 
cause of  its  low-lying  position  the  type  is  not  well  adapted  to  fruit 
culture.  Large  areas  are  unproductive  because  of  the  excessive  ac- 
cumulations of  alkali,  but  in  the  eastern  part  of  the  area  less  alkali 
is  present,  arid  the  white  farmers  here  produce  good  crops  of  grain. 
The  Indians  get  only  fair  yields  on  this  type,  considerably  below 
those  obtained  by  the  white  farmers.  The  uncultivated  areas  of  the 
type  are  used  as  pastures.  All  crops  are  grown  under  irrigation, 
water  being  obtained  from  the  Gila  River  and  by  ])umping  from 
wells.  Much  of  this  type  within  the  Indian  reservation  is  under  a 
canal  system  installed  by  the  Government.  Reclamation  is  accom- 
plished by  checking  the  land  and  flooding  it  for  several  months  or  for 
several  seasons,  depending  upon  the  concentration  of  salts.  Much  of 
the  type  requires  artificial  drainage.  No  fertilizers  are  used  and  crop 
rotations  are  seldom  followed. 

The  price  of  land  of  this  type  depends  largely  upon  its  condition 
for  farming  and  the  location.  Little  of  it  has  changed  hands  re- 
cently and  the  Indian  lands  are  not  sold.    Prices  range  from  as  low 


28 


FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 


as  $5  or  $10  an  acre  to  $100  an  acre  where  <;ood  stands  of  grain  can 
be  obtained. 

The  table  below  gives  the  resnlts  of  mechanical  analyses  of  samples 
of  the  soil  and  subsoil  of  the  Gila  silty  clay  loam  : 

MccliiHik-dl  an(iJii!<ci<  of  fUla  .s(7///  chn/  loam. 


Number. 

I>escriptlon. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
saud. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

510405 

Soil 

Per  cent. 
0.1 
.0 

Per  cent. 

0.4 

.2 

Per  cent. 

().3 

.1 

Per  cent. 
3.4 
6.1 

Per  cent. 
18.2 
22.3 

Per  cent. 
53.2 
48.0 

Per  cent. 
24.3 

510406 

Subsoil 

23.1 

PIMA   CLAY. 


The  soil  of  the  Pima  clay  consists  of  a  dark-brown  or  dark  gi-ayish 
brown  clay,  in  many  places  relatively  high  in  silt,  18  to  24  inches 
deep.  It  is  sticky  when  wet  and  cracks  when  dry,  but  it  contains 
much  organic  matter  and  retains  moisture  well.  The  type  through- 
out contains  a  large  amount  of  lime.  The  subsoil  is  a  light  grayish 
brown  silty  clay  loam  to  clay,  extending  to  a  depth  of  more  than  C 
feet.  It  differs  from  the  surface  soil  in  its  lighter  color,  and  in  being 
compact,  but  it  has  not  been  materially  changed  by  leaching,  cementa- 
tion, or  weathering  in  place.  Small  areas  here  and  there  are  under- 
lain by  gravel  or  sand  at  a  depth  of  several  feet,  which  alloAVS  the 
water  to  penetrate  more  rapidly,  and  a  gravelly  substratum  underlies 
the  type  at  various  depths. 

The  Pima  clay  is  not  extensive,  but  it  is  important  in  the  agricul- 
ture of  the  area.  The  type  is  confined  to  the  flood  plain  of  the  Gila 
Kiver,  where  it  occurs  in  irregular-shaped  areas  or  in  long,  narrow 
strips,  generally  roughly  paralleling  the  stream.  It  is  found  in  all 
parts  of  the  valley  from  the  eastern  to  the  western  boundary  of  the 
area. 

The  surface  is  level  or  slightly  depressed.  Flood  water  stands  on 
the  surface  until  removed  by  percolation  or  evaporation.  This  is  a 
slow  process,  and  more  time  must  elapse  between  overflows  and  culti- 
vation than  in  case  of  some  of  the  other  bottom  soils.  The  type  main- 
tains a  better  moisture  supply  during  droughts  than  the  river-bottom 
soils  of  lighter  texture.  Parts  of  the  type  contain  alkali,  but  in- 
jurious accumulations  are  less  common  than  in  the  Gila  silty  clay 
loam.  The  type  is  not  directly  overflowed  by  the  river,  the  water 
coming  from  other  sources.  Water  is  easily  applied  in  irrigation, 
and  much  of  the  type  is  under  gravity  canals. 

In  most  places  the  vegetation  consists  mainly  of  a  heavy  growth  of 
mescpiite,  but  Avhere  alkali  is  present  such  plants  as  greasewood,  salt- 
bush,  and  salt  grass  grow. 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA. 


29 


Many  of  the  Indian  farmers  cultivate  parts  of  the  Pima  clay, 
buildinjj  their  towns  and  houses  on  the  adjoinin<;  terraces  of  Gila 
silty  clay  loam,  which  are  generally  affected  by  alkali.  Wheat,  bar- 
ley, alfalfa  (PL  II,  fig.  2),  corn,  hay,  sorghum,  truck,  and  root  crops 
are  grown,  and  good  yields  are  obtained.  None  of  the  farmers  use 
fertilizer,  and  no  crop  rotation  is  followed.  The  type  brings  as  high 
prices  as  any  in  the  Gila  Yalley. 

In  the  table  below  are  given  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Pima  clay : 

Mechanical  analyses  of  Pima  clay. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

510415 

Soil 

Per  cent. 

0.1 

.0 

Per  cent. 

0.5 

.1 

Per  cent. 

0.2 

.0 

Per  cent. 
3.1 

2.8 

Per  cent. 
4.7 
IS.  6 

Per  cent. 
37.0 
52.7 

Per  cent. 
54.4 

510416 

25.8 

BOUGH  STONY  LAND. 

Rough  stony  land  consists  of  steep,  rough,  and  stony  areas  that 
have  no  present  agricultural  value.  It  includes  various  shallow  soils 
occupying  buttes  and  the  lower  slopes  of  mountains.  The  soils  are 
of  residual  origin,  and  derived  almost  entirely  from  granite,  gneiss, 
mica  schist,  and  associated  rocks.  There  are  numerous  outcropping 
ledges,  and  loose  stones  and  rock  fragments  of  all  sizes  are  abundant, 
especially  around  the  lower  slopes  of  the  buttes  and  mountains. 

This  type  is  of  small  extent,  as  the  survey  covers  only  the  most 
desirable  agricultural  lands  of  the  region.  The  most  important  areas 
lie  southeast  of  Casa  Grande,  at  Twin  Butte,  and  on  Cholla  Moun- 
tain. Smaller  areas  are  mapped  on  small  buttes  within  the  area, 
and  on  parts  of  the  hill  and  mountain  slopes. 

The  vegetation  over  the  greater  part  of  the  Rough  stony  land  is 
sparse  and  of  low  grazing  value.  It  consists  mainly  of  cacti  of  vari- 
ous kinds,  creosote  bush,  and  several  other  unimportant  plants. 

RIVERWASH. 

Riverwash  consists  of  the  material  occupying  the  bed  of  the  Gila 
River.  The  soil  is  a  mixture  of  coarse,  medium,  and  fine  sands, 
together  with  some  finer  sediments,  and  differs  chiefly  from  the 
Riverwash  of  the  Solomonsville  area,  in  the  Upper  Gila  Valley,  in 
carrying  less  gravel,  stones,  and  coarse  sandy  material.  The  type  is 
usually  more  silty  along  the  edges  of  the  stream  bed,  where  the 
current  is  sluggish. 

The  boundaries  of  the  strip  of  Riverwash  are  very  irregular,  and 
in  many  places  they  are  drawn  rather  arbitrarily.    The  surface  of 


30  FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1917. 

the  type  is  smooth,  with  a  very  gentle  gradient  toward  the  stream. 
It  is  flood-swept  during  periods  of  high  water  and  during  tlie  rainy 
season,  and  at  all  times  the  water  table  is  high.  The  type  is  of  no 
present  agricultural  importance. 

IRRIGATION. 

Irrigation  is  necessary  in  the  Middle  Gila  Valley  area  because  of 
the  low  rainfall  and  the  long  dry  seasons.  The  Indians  practiced 
irrigation  before  the  coming  of  the  white  man,  using  a  rude  system 
of  canals  to  take  water  from  the  river  and  distribute  it  over  the  river 
bottoms  and  near-by  desert  slopes.  The  1910  census  reports  a  total 
of  89,400  acres  in  Pinal  County  embraced  in  irrigation  projeets,  but 
only  25,431  acres  actually  irrigated,  of  which  13,831  acres  were  sup- 
plied with  water  by  partnership  and  individual  enterprises,  3,500 
acres  by  cooperative  enterprises,  and  8,000  acres  under  the  Indian 
Reservation  project.  The  irrigated  acreage  for  Pinal  County  is 
practically  all  Avithin  the  limits  of  the  present  survey.  Nearly  all 
the  water  for  irrigation  is  drawn  from  the  Gila  River  by  gravity 
canals.  In  1917,  9,000  acres  were  under  irrigation  on  the  units  of 
the  Indian  Reservation  within  the  present  survey. 

The  Gila  River  is  a  broad  stream,  with  poorly  defined  banks 
throughout  most  of  its  course.  During  the  rainy  season  gi'eat 
volumes  of  water  fill  the  channel  and  overfloAv  the  banks,  but  during 
the  dry  season  its  sandy  bed  is  bare.  In  the  absence  of  a  storage 
supply,  irrigation  from  the  river  is  impossible  during  parts  of  the 
year. 

The  water  of  the  Gila  River  is  of  good  quality  for  irrigation,  the 
flood  Avaters  containing  only  small  amounts  of  soluble  salts.  A 
sample  of  such  water  taken  at  Florence  contained  68  parts  of  soluble 
salts  per  100,000,  but  during  normal  flow  the  water  is  slightly  higher 
in  salts.  The  river  water  is  very  high  in  silt,  and  the  flood  waters 
carry  in  addition  much  organic  matter  washed  from  mountain  slopes 
by  the  torrential  rains.  These  sediments  are  deposited  on  the  soils 
by  irrigation  and  overflow  waters,  and  while  some  inconvenience  is 
caused  by  the  rapid  and  frequent  silting  up  of  canals,  much  benefit 
results  from  such  deposits,  especially  in  the  case  of  the  desert  soils  of 
light  texture  and  Ioav  organic  content.  The  continued  use  of  the 
silty  irrigation  water  even  improves  the  texture  of  the  lighter  soils. 

During  the  last  few  years  many  wells  have  been  sunk  for  irriga- 
tion purposes  in  various  parts  of  the  river  bottoms,  and  a  few  in  the 
adjacent  areas  of  old  valley-filling  soils  of  the  desert.  In  most  in- 
stances a  good  supply  of  water  has  been  obtained,  the  shallower 
wells  in  the  stream  bottoms  furnishing  a  more  abundant  su]i])ly  than 
the  wells  in  the  desert  areas.  Water  obtained  in  the  desert  sections 
generally  is  of  good  quality,  usually  containing  less  than  50  parts 


SOIL  SURVEY   OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  31 

of  soluble  salts  per  100,000.  The  water  from  wells  in  the  river  bot- 
tom is  usually  higher  in  soluble  salts,  the  proportion  ranging  from 
120  to  160  parts  per  100,000.  In  a  numl)er  of  instances  there  are 
indications  of  sodium  carbonate.  Most  of  the  wells  in  the  desert 
section  tap  a  strata  giving  moderate  supply  of  water  at  depths  rang- 
ing from  125  feet  downward,  the  water  rising  in  the  wells  to  within 
35  feet  of  the  surface. 

The  United  States  Indian  Office  has  quite  thoroughly  investigated 
and  developed  the  water  supply  for  parts  of  the  Indian  reservation 
within  the  area.  Most  of  the  water  is  obtained  from  the  Gila  River 
and  conducted  to  the  land  by  a  system  of  main  ditches  and  laterals, 
wells  supplementing  the  gravity  water  supply  during  the  dry  season. 
A  series  of  nine  wells  supplying  25  second- feet  extends  across  the 
Santan  District,  and  furnishes  water  for  a  main  ditch  when  the 
river  supply  is  short.  A  well  at  Sacaton  supplements  the  river  sup- 
ply for  the  experimental  farm  of  the  Bureau  of  Plant  Industry  and 
that  of  the  Indian  agency.  Another  series  of  wells  is  used  to  irri- 
gate the  United  States  Indian  seed  farm  near  Sacaton,  no  gravity 
water  being  applied. 

The  amount  of  water  necessary  to  mature  crops  in  this  region  de- 
pends largely  on  the  situation  of  the  land,  the  nature  of  the  soil,  and 
the  crop  grown.  Areas  in  the  river  bottoms  require  less  water  than 
those  in  the  desert,  and  the  heavier  textured  soils  produce  good  yields 
with  less  water  than  the  types  of  more  open  structure.  Many  of  the 
bottom  lands  are  naturally  subirrigated,  but  this  condition  is  likely 
to  be  accompanied  by  accumulations  of  alkali,  which  is  brought  to 
the  surface  through  the  capillary  rise  and  evaporation  of  soil  water. 
Surface  irrigation  is  beneficial  on  the  subirrigated  soils,  as  this  tends 
to  wash  the  salts  into  the  subsoil. 

Alfalfa  requires  much  w  ater  for  maximum  yields,  one  flooding  for 
each  cutting  being  necessary  during  the  dry  season.  Other  crops 
such  as  grain  and  grain  hay  require  less  water,  as  they  mature  early. 
Cultivated  crops  like  corn,  cotton,  truck,  and  tree  fruits  require  water 
during  the  growing  season,  and  this  is  applied  by  the  furrow  method. 

Most  of  the  irrigated  land  lies  in  the  Gila  River  bottoms  and  in- 
cludes Indian  allotments  as  w^ell  as  large  ranches.  Only  small 
patches  are  cultivated  in  the  desert  section,  but  farming  centers  are 
developing  in  the  vicinity  of  Florence  and  Casa  Grande.  The  de- 
velopment of  the  greater  part  of  the  agricultural  area  outside  the 
stream  bottoms  will  i^robably  depend  upon  effective  storage  of  the 
Gila  River  waters. 

DRAINAGE. 

The  natural  drainage  in  the  Gila  River  bottoms,  where  most  of  the 
agricultural  development  has  taken  place,  is  poor.    These  lands  lie 


32 


FIELD   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   19V1. 


onl}'  a  little  above  the  channel  of  the  stream.  An  nndei-lyino^ 
stratum  of  gravel  and  sand  permits  of  the  ready  movement  of  under- 
ground water,  and  there  is  generally  a  high  water  tal)le.  The  poor 
drainage  of  the  bottoms  is  further  accentuated  by  seepage  from  irri- 
gation upon  adjacent  terraces  or  uplands  and  by  the  underground 
flow  from  tributary  creeks  and  drainage  ways.  The  latter  is  of  im- 
portance in  numerous  places,  but  is  especially  pronounced  at  the  place 
where  the  McClellan  Wash  enters  the  Gila  River  bottoms.  Drainage 
is  also  poorly  developed  locally  in  the  shallow  and  imperfect  drain- 
age ways  of  the  desert.  Here  the  gradient  is  low,  and  the  run-oif 
and  percolation  much  retarded.  The  greater  surface  slope  and  more 
pervious  subsoils  of  the  bottoms  make  the  drainage  more  perfect  than 
in  the  case  of  the  low,  flat  desert  areas  of  old  valley-filling  soils,  with 
their  slight  slope  and  dense  compacted  subsoil.  The  high  water 
table  of  the  bottoms  is  often  relieved  by  open  ditches  and  sometimes 
by  tile  drains.  Little  attempt  has  been  made  to  provide  drainage 
for  the  broad  flats  of  the  desert,  cultivation  being  confined  to  the 
better  drained  soils. 

ALKALI. 

The  Middle  Gila  Valley  area  is  situated  in  an  arid  region  of 
excessive  evaporation,  where  soluble  salts  are  readily  accumulated. 
More  than  50  per  cent  of  the  area  is  more  or  less  affected  by  alkali 
accumulation.  The  following  table  shows  the  results  of  an  analysis 
of  a  composite  sample  of  alkali  crust  taken  in  various  parts  of  the 
survey : 

Chemical  analysis  of  alkali  crust. 

[Parts  per  100,000.] 


Constituent. 

Quantity. 

Constituent. 

Quantity. 

Ions: 

Mg 

Trace. 

16,673 

208 

8,408 

16,080 

424 

2,792 

Trace. 

Conventional  combinations: 
CaS04 

Trace. 

Na 

MgSOi 

Trace 

K 

K2S04    . 

463 

S0< 

NajSOi  . 

12  066 

CI 

NaCl. 

26  535 

ncoa 

NalTCOj      

584 

C03 

Na2C03 

4  937 

Ca 

The  above  re.sults  show  that  sodium  chloride,  sodium  sulphate,  and 
sodium  carbonate  predominate  in  the  alkali  of  this  area.  Sodium 
chloride,  or  common  salt,  is  by  far  the  most  abundant,  composing  a 
little  more  than  25  per  cent  of  the  average  crust.  The  sodium  sul- 
phate constitutes  a  little  over  12  per  cent,  while  the  proportion  of 
sodium  carbonate,  commonly  known  as  black  alkali,  is  less  than  5  per 


SOIL   SURVEY   OF   THE    MIDDLE   GILA  VALLEY,   ARIZON^A.  33 

cent.  A  very  small  proportion  of  sodium  bicarbonate  is  also  present. 
Of  the  principal  bases  which  combine  to  form  the  alkali  salts,  sodium 
is  the  only  one  of  importance  represented  in  the  surface  crust. 
Potassium,  magnesium,  and  calcium  exist  only  in  very  small 
amounts,  or  traces. 

The  alkali  salts  are  all  highly  soluble  and  their  presence  in  the 
surface  soil  is  due  principally  to  the  evaporation  of  soil  waters. 
They  have  for  the  most  part  been  transported  to  the  localities  in 
wdiich  they  occur  by  subsurface  and  surface  drainage  waters  carrying 
them  in  solution. 

The  conditions  of  drainage  in  the  bottom  soils  differ  from  those  in 
the  upland  or  desert  soils.  The  soils  of  the  Gila  River  bottoms,  as 
has  been  pointed  out,  are  affected  by  seepage  and  have  a  high  water 
table ;  this,  with  their  texture  and  structure,  which  favor  capillarity, 
has  caused  the  large  accumulations  in  the  valley.  The  heavy  alkali 
crusts  formed  during  the  dry  season  are  partly  removed  in  surface 
drainage  waters  or  are  carried  downward  during  the  rainy  period. 

The  desert  or  upland  soils  generally  have  impervious  subsoil  lay- 
ers, and  where  they  are  affected  by  alkali,  little  free  movement  of  the 
salts  in  subsurface  waters  is  possible.  In  many  places  the  crusts  of 
surface  salts  are  very  thin  even  during  the  driest  season,  although 
the  areas  are  barren  of  vegetation  and  the  total  average  alkali  con- 
tent high.  Many  of  the  barren  alkali  flats  are  interrupted  or  bordered 
by  slightly  higher  lying  soils  of  lighter  texture,  which  are  frequently 
free  from  surface  accumulations  of  alkali.  The  flats  receive  run-off 
from  the  adjacent  soils,  and  the  water  remains  until  removed  by 
evaporation  or  percolation.  Both  the  suspended  sediments  and  the 
salts  in  solution  are  deposited,  and  upon  drying  form  a  smooth,  hard, 
surface  which  greatly  retards  the  movement  of  the  salts. 

Owing  to  these  different  conditions  the  distribution  of  alkali  salts 
in  the  6-foot  profile  varies  greatly  with  the  different  soils  and  situa- 
tions. Alkali  in  general  is  more  uniformly  distributed  through  the 
soil  profile  in  the  recent-alluvial  soils  than  in  the  old  valley-filling  or 
desert  types  with  compacted  subsoils.  Where  the  distribution  is  un- 
equal, the  zone  of  maximum  concentration  usually  lies  between  the 
first  and  third  feet  in  the  recent-alluvial  soils,  while  in  the  desert 
types  the  zone  of  highest  salt  content  is  usually  deeper. 

The  distribution  and  degree  of  concentration  of  the  alkali  areas  are 
shown  on  the  accompanying  alkali  map.  The  mapping  is  based  upon 
field  determinations  with  the  electrolytic  bridge  method.  The  aver- 
age salt  content  of  the  6-foot  profile,  based  upon  the  content  of  each 
foot  section,  is  determined.  The  results  are  expressed  in  terms  of 
parts  per  100,000.  Five  grades  of  alkali  land  are  shown.  Grade  A 
comprises  soils  in  which  the  average  concentration  of  salt  is  under 


34  FIELD   OPEKATIONS   OF   THE   BUREAU   OF   SOILS,  1917. 

200  parts  per  100,000  of  air-dry  soil;  jrrade  B  represents  soils  con- 
tainiii<r  between  200  and  400  parts;  j^rade  C  betAveen  400  and  GOO 
parts;  grade  D  between  600  and  1,000  parts;  and  grade  E  those  con- 
taining over  1,000  parts. 

Alkali  conditions  in  the  field  are  indicated  largely  by  surface  ap- 
pearance, vegetation,  and  topography,  and  the  differentation  of  the 
alkali  soils  into  the  above  grades  is  aided  largely  by  field  observa- 
tions of  these  factors.  On  soils  free  from  alkali  or  possessing  only 
small  amounts  in  the  root-feeding  zone,  such  native  plants  as  desert 
sage, creosote  bush,  rabbit  brush, and  several  \arieties  of  cactus  thrive. 
On  the  more  heavily  impregnated  soils  squaw-bush,  salt-blight, 
greasewo"od,  and  pickleweed  grow.  Of  course,  where  alkali  is  con- 
centrated in  the  sul)soil  the  vegetation  is  not  a  safe  guide,  but  enough 
checks  are  made  with  the  bridge  to  guard  against  mistake  of  this 
kind. 

The  areas  of  alkali  soil  increase  in  size  and  in  degree  of  salt 
concentration  as  the  lower  levels  to  the  west  are  approached.  Many 
of  the  flat,  shallow  valleys  that  traverse  the  area  in  a  northwesterlj'^ 
direction  have  only  slight  indications  of  alkali  at  their  higher  levels, 
but  include  areas  of  high  alkali  concentration  in  their  lower  reaches. 
WTiile  much  of  the  soil  of  the  Gila  River  bottoms  below  Blackwater 
contains  alkali,  alkali-free  areas  occur  in  places.  Above  Blackwater. 
the  alkali  areas  are  smaller  and  of  less  importance.  The  immediate 
overflow  plain  of  the  Gila  River  is  little  affected  by  alkali,  the  low 
terrace  between  the  overflow  plain  and  the  uplands  containing  the 
areas  of  highest  concentration.  The  largest  alkali-free  areas  lie  in 
the  southern  part  of  the  survey,  between  McClellan  Wash  and  Casa 
Grande,  and  east  and  northeast  of  McClellan  Wash.  An  extensive 
alkali-free  area  roughly  parallels  the  Southern  Pacific  Railroad. 
The  slopes  about  the  mountains  and  foothills  are  generally  free  from 
injurious  amounts  of  alkali,  except  in  the  vicinity  of  seepage 
channels.  Plate  A  shows  tlie  general  distribution  of  alkali  lands  in 
the  area. 

All  of  the  soil  types  except  the  Pinal  gravelly  sandy  loam  arc 
affected  in  places  by  alkali.  The  Gila  fine  sand  and  silty  clay  loam 
frequently  contain  injurious  amounts,  but  the  Pima  clay,  one  of  the 
important  agricultural  soils,  generally  contains  only  small  amounts. 
The  McClellan  loam,  silty  phase,  is  free  from  alkali,  while  the  shal- 
low phase  of  the  same  type  generally  contains  varying  amounts. 
The  Mohave  sandy  loam  and  fine  sandy  loam  are  generally  well 
drained  and  contain  alkali  only  locally  or  in  the  marginal  zones  of 
the  areas. 

Prioi-  to  the  coming  of  the  white  man  the  Indian  reclaimed  small 
patches  of  land  in  the  Gila  River  bottoms,  using  the  floodwater  of 
the  (Jila   River  for  irrigation.     In   manv   instances  lands  high   in 


SOIL  SURVEY  OF   THE   MIDDLE   GILA  VALLEY,   ARIZONA.  35 

concentration  of  salts  were  brought  to  a  productive  state  by  repeated 
flooding  over  several  seasons,  and  further  improved  by  irrigation  and 
cultivation. 

The  elevation  and  sul)soil  characteristics  of  the  alkali  lands  greatly 
influence  the  possibility  of  reclamation.  The  mere  flooding  of  the 
upland  soils  frequently  removes  enough  alkali  to  permit  the  growing 
of  crops,  where  the  subsoil  is  not  too  compact  and  impervious,  but  in 
the  bottoms  the  usually  high  water  table  must  be  lowered  by  resort- 
ing to  artificial  drainage  before  the  lands  can  be  permanently  re- 
claimed. Many  tracts  of  land  in  the  Gila  bottoms  have  been  made 
productive  merely  by  repeated  flooding,  but  when  cultivation  and 
irrigation  cease  for  several  seasons  these  soils  tend  to  revert  to  their 
former  condition.  Soils  containing  small  amounts  of  alkali,  evident 
only  in  level  spots,  produce  well  when  properly  cultivated  and  irri- 
gated. In  upland  areas  of  high  salt  concentration  where  there  is  an 
impervious  subsoil  several  feet  in  thiclmess,  and  in  many  of  the  badly 
affected  bottom  soils,  the  cost  of  permanent  reclamation  by  means  of 
drainage  and  flooding  is  prohibitive  under  present  economic  con- 
ditions. 

SUMMARY. 

The  Middle  Gila  Valley  area  includes  the  bottom  and  terrace  lands 
of  the  Gila  River  from  a  point  about  5  miles  northeast  of  Florence 
to  Sacate  and  a  part  of  the  desert  plains  east  and  south  of  the  Sacaton 
Mountains.  Almost  all  the  territory  lies  in  Pinal  County.  The 
survey  covers  352  square  miles,  or  225,280  acres. 

Elevations  range  between  1,150  feet  and  1,525  feet  above  sea  level. 
Several  small  buttes  within  the  area  and  the  included  parts  of  the 
adjacent  mountain  slopes  are  stony  and  of  little  agricultural  value. 

The  Gila  Eiver  is  the  principal  drainage  way  in  this  part  of  the 
vState.  McClellan  Wash  and  Santa  Cruz  Wash  drain  the  greater 
part  of  the  desert  plains  within  the  area.  The  channel  of  the  Gila 
River  is  broad,  with  poorly  defined  banks,  and  overflows  are  frequent. 
The  channels  of  the  McClellan  and  Santa  Cruz  Washes  are  poorly 
defined  and  have  little  fall,  much  land  being  flooded  at  irregular 
storm  periods  along  their  courses. 

The  population  of  Pinal  County  in  1910  was  9,045.  Nearly  one- 
third  of  this  consisted  of  Indians  on  the  Gila  River  Indian  Reserva- 
tion. There  are  many  Mexicans  and  small  numbers  of  Negroes,  Chi- 
nese, and  Japanese.  There  are  two  incorporated  towns  in  the  area 
and  several  Indian  villages.  Florence  is  the  largest  town  and  the 
county  seat  of  Pinal  County. 

The  Southern  Pacific  Railroad  and  the  Arizona  Eastern  Railway 
touch  the  area,  but  most  of  the  farms  are  remote  from  shipping 
points. 


36  FIELD   OPERATIOjSTS   OF   THE   BUREAU   OF   SOILS,   1917. 

The  climate  is  warm  and  arid.  The  mean  annual  precipitation  at 
Phoenix  is  6.8  inches  and  at  Maricopa  6.24  inches.  Two  wet  seasons 
occur,  one  in  the  sprino^  and  one  in  the  late  summer.  The  mean  an- 
nual temperature  at  Maricopa  is  69.6°,  Maximum  temperatures  as 
recorded  at  this  station  range  between  110°  and  126°.  The  lowest 
temperatures  are  usually  above  25°,  but  a  minimum  of  8°  has  been 
recorded.  The  average  date  of  the  last  killing  frost  in  the  spring  is 
March  7,  and  that  of  the  earliest  in  the  fall,  November  27. 

Irrigated  farming  was  carried  on  in  the  Gila  Valley  by  prehistoric 
races,  and  by  Indians  for  centuries  preceding  settlemept  by  the 
whites.  Grain  was  the  chief  crop  grown  by  the  Indians,  and  is  still 
very  important. 

The  principal  agricultural  products  are  cereals,  chiefly  wheat,  hay, 
mainly  alfalfa,  and  live  stock.  Corn  is  grown  to  some  extent. 
Egyptian  corn  and  milo  are  becoming  important  crops.  Long-staple 
Egyptian  cotton  has  been  introduced  and  promises  to  become  a  very 
im]:>ortant  money  crop  with  both  white  farmers  and  Indians. 

The  methods  in  use  by  the  white  farmers  are  good,  but  the  Indian 
is  slow  to  adopt  modern  methods  and  machinery. 

The  i^ossibility  of  irrigation  and  presence  of  alkali  have  had  more 
influence  on  the  distribution  of  crops  than  has  soil  character. 

The  Pima  Indians  and  Mexicans  supply  most  of  the  farm  labor. 
Over  95  per  cent  of  the  farms  were  operated  by  the  owners. 

The  soils  of  the  Middle  Gila  Valley  fall  into  three  main  groups — 
residual,  old  valley  filling,  and  recent  alluvial.  The  old  valley-filling 
group  is  most  extensive,  and  includes  the  desert  or  upland  soils.  The 
recent-alluvial  group  includes  the  soils  at  present  of  greatest  agri- 
cultural value.  The  residual  group  is  unimportant,  including  the  one 
nonagricultural  type,  Eough  stony  land. 

Five  series,  including  eight  soil  types,  are  recognized  and  mapped 
in  this  area,  in  addition  to  Eough  stony  land  and  Riverwasli.  The  old 
.  valley-filling  soils  cover  about  75  per  cent  of  the  area.  They  are 
derived  from  weathered  and  altered  old-alluvial  deposits,  and  are 
characterized  by  a  limy,  compacted  or  cemented  subsoil  or  hardpan. 
The  surface  is  smooth  or  undulating.  Three  soil  series  are  recognized 
under  this  group,  the  Pinal,  Mohave,  and  McClellan. 

The  Pinal  gravell}^  sandy  loam  has  a  cemented,  gravelly  hardpan. 
The  Mohave  series  consists  of  light-textured,  red  or  reddish-brown 
soils,  with  a  compact  subsoil  approaching  a  hardpan.  Two  types, 
in  which  some  alkali  occurs,  are  included  in  this  series.  The  McClel- 
lan series  is  darker  and  browner  in  color  than  the  Mohave.  Two 
types  are  included,  the  heavier  of  which  has  a  level  surface  and  con- 
tains alkali. 

The  recent-alluvial  soils,  confined  to  the  bottoms  and  low  terraces 
of  the  Gila  River,  are  classified  with  the  Gila  and  Pima  series.    These 


SOIL   SURVEY    OF     CHE    MIDDLE    GILA   VALLEY,    ARIZONA.  o7 

tj^pes  liHve  more  friable  subsoils,  contain  more  organic  matter,  and 
are  more  poorly  drained  than  those  of  the  old  valley-filling  group. 
The  Gila  soils  are  brown  and  underlain  by  a  permeable  subsoil;  the 
soils  of  the  Pima  series  have  similar  characteristics  except  color, 
Avhich  is  darker.  Alkali  is  present  in  places  in  both  these  series.  The 
soils  are  overflowed  and  have  a  high  water  table. 

Irrigation  is  necessary  to  insure  crops  in  this  region.  In  1910 
there  were  25,431  acres  under  irrigation.  Practically  all  the  water 
for  irrigation  is  obtained  by  gravity  from  the  Gila  Kiver.  This  is 
generally  of  good  quality.  Water  is  also  obtained  from  wells.  This 
may  be  somewhat  higher  in  soluble  salts  than  the  river  water.  Stor- 
age of  the  waters  of  the  Gila  River  is  necessary  to  the  permanent 
development  of  the  desert  lands. 

More  than  50  per  cent  of  the  lands  in  this  area  contain  more  or 
less  alkali.  Sodium  chloride,  sodium  sulphate,  and  sodium  carbonate 
predominate  in  the  alkali  crust.  Sodium  chloride  is  by  far  the  most 
abundant.  The  chief  alkali  areas  occur  at  the  lower  levels,  in  the 
western  and  southwestern  parts  of  the  survey.  The  largest  alkali - 
free  areas  occur  northeast  and  east  and  to  the  west  of  McClellan 
Wash,  Alkali-free  areas  also  occur  along  the  Southern  Pacific  Rail- 
road and  on  the  mountain  and  foothill  slopes. 

o 


5DJL  MAP 


5^ 

r- 

'wa_- 

i=t:is~ 

^^ 

sarj; 

[Public  Resolution — ^No.  9.] 

JOINT  RESOLUTION  Amending  public  resolution  numbered  eight,  Fifty-sixth  Congress, 
second  session,  approved  February  twenty-third,  nineteen  hundred  and  one,  "  providing 
for  the  printing  annually  of  the  report  on  field  operations  of  the  Division  of  Soils, 
Department  of  Agriculture." 

Resolved  hy  the  Senate  and  House  of  Representatives  of  the  United  States  of 
America  in  Congress  assembled,  That  public  resolution  numbered  eight,  Fifty- 
sixth  Congress,  second  session,  approved  February  twenty-third,  nineteen  hun- 
dred and  one,  be  amended  by  striking  out  all  after  the  resolving  clause  and  in- 
serting in  lieu  thereof  the  following: 

That  there  shall  be  printed  ten  thousand  five  hundred  copies  of  the  report  on 
field  operations  of  the  Division  of  Soils,  Department  of  Agriculture,  of  which 
one  thousand  five  hundred  copies  shall  be  for  the  use  of  the  Senate,  three  thou- 
sand copies  for  the  use  of  the  House  of  Representatives,  and  six  thousand  copies 
for  the  use  of  the  Department  of  Agriculture :  Provided,  That  in  addition  to  the 
number  of  copies  above  provided  for  there  shall  be  printed,  as  soon  as  the 
manuscript  can  be  prepared,  with  the  necessary  maps  and  illustrations  to  accom- 
pany it,  a  report  on  each  area  surveyed,  in  the  form  of  advance  sheets,  bound 
in  paper  covers,  of  which  five  hundred  copies  shall  be  for  the  use  of  each  Sena- 
tor from  the  State,  two  thousand  copies  for  the  use  of  each  Representative  for 
the  congressional  district  or  districts  in  which  the  survey  is  made,  and  one 
thousand  copies  for  the  use  of  the  Department  of  Agriculture. 

Approved,  March  14,  1904. 

[On  July  1,  1901,  the  Division  of  Soils  was  reorganized  as  the  Bureau  of  Soils.] 


MOHAVE 


APACHE 


Areas  surveyed  in  Arizona. 


